Vaccines for preventing influenza in healthy children

Vaccines for the common cold

BACKGROUND

The common cold is a spontaneously remitting infection of the upper respiratory tract, characterised by a runny nose, nasal congestion, sneezing, cough, malaise, sore throat, and fever (usually < 37.8 ºC). Whilst the common cold is generally not harmful, it is a cause of economic burden due to school and work absenteeism. In the United States, economic loss due to the common cold is estimated at more than USD 40 billion per year, including an estimate of 70 million workdays missed by employees, 189 million school days missed by children, and 126 million workdays missed by parents caring for children with a cold. Additionally, data from Europe show that the total cost per episode may be up to EUR 1102. There is also a large expenditure due to inappropriate antimicrobial prescription. Vaccine development for the common cold has been difficult due to antigenic variability of the common cold viruses; even bacteria can act as infective agents. Uncertainty remains regarding the efficacy and safety of interventions for preventing the common cold in healthy people, thus we performed an update of this Cochrane Review, which was first published in 2011 and updated in 2013 and 2017.

OBJECTIVES

To assess the clinical effectiveness and safety of vaccines for preventing the common cold in healthy people.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (April 2022), MEDLINE (1948 to April 2022), Embase (1974 to April 2022), CINAHL (1981 to April 2022), and LILACS (1982 to April 2022). We also searched three trials registers for ongoing studies, and four websites for additional trials (April 2022). We did not impose any language or date restrictions.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of any virus vaccine compared with placebo to prevent the common cold in healthy people.

DATA COLLECTION AND ANALYSIS

We used Cochrane's Screen4Me workflow to assess the initial search results. Four review authors independently performed title and abstract screening to identify potentially relevant studies. We retrieved the full-text articles for those studies deemed potentially relevant, and the review authors independently screened the full-text reports for inclusion in the review, recording reasons for exclusion of the excluded studies. Any disagreements were resolved by discussion or by consulting a third review author when needed. Two review authors independently collected data on a data extraction form, resolving any disagreements by consensus or by involving a third review author. We double-checked data transferred into Review Manager 5 software. Three review authors independently assessed risk of bias using RoB 1 tool as outlined in the Cochrane Handbook for Systematic Reviews of Interventions. We carried out statistical analysis using Review Manager 5. We did not conduct a meta-analysis, and we did not assess publication bias. We used GRADEpro GDT software to assess the certainty of the evidence and to create a summary of findings table.  MAIN RESULTS: We did not identify any new RCTs for inclusion in this update. This review includes one RCT conducted in 1965 with an overall high risk of bias. The RCT included 2307 healthy young men in a military facility, all of whom were included in the analyses, and compared the effect of three adenovirus vaccines (live, inactivated type 4, and inactivated type 4 and 7) against a placebo (injection of physiological saline or gelatin capsule). There were 13 (1.14%) events in 1139 participants in the vaccine group, and 14 (1.19%) events in 1168 participants in the placebo group. Overall, we do not know if there is a difference between the adenovirus vaccine and placebo in reducing the incidence of the common cold (risk ratio 0.95, 95% confidence interval 0.45 to 2.02; very low-certainty evidence). Furthermore, no difference in adverse events when comparing live vaccine preparation with placebo was reported. We downgraded the certainty of the evidence to very low due to unclear risk of bias, indirectness because the population of this study was only young men, and imprecision because confidence intervals were wide and the number of events was low. The included study did not assess vaccine-related or all-cause mortality.  AUTHORS' CONCLUSIONS: This Cochrane Review was based on one study with very low-certainty evidence, which showed that there may be no difference between the adenovirus vaccine and placebo in reducing the incidence of the common cold. We identified a need for well-designed, adequately powered RCTs to investigate vaccines for the common cold in healthy people. Future trials on interventions for preventing the common cold should assess a variety of virus vaccines for this condition, and should measure such outcomes as common cold incidence, vaccine safety, and mortality (all-cause and related to the vaccine).

An empirical evaluation of the impact scenario of pooling bodies of evidence from randomized controlled trials and cohort studies in medical research

BACKGROUND

Randomized controlled trials (RCTs) and cohort studies are the most common study design types used to assess treatment effects of medical interventions. We aimed to hypothetically pool bodies of evidence (BoE) from RCTs with matched BoE from cohort studies included in the same systematic review.

METHODS

BoE derived from systematic reviews of RCTs and cohort studies published in the 13 medical journals with the highest impact factor were considered. We re-analyzed effect estimates of the included systematic reviews by pooling BoE from RCTs with BoE from cohort studies using random and common effects models. We evaluated statistical heterogeneity, 95% prediction intervals, weight of BoE from RCTs to the pooled estimate, and whether integration of BoE from cohort studies modified the conclusion from BoE of RCTs.

RESULTS

Overall, 118 BoE-pairs based on 653 RCTs and 804 cohort studies were pooled. By pooling BoE from RCTs and cohort studies with a random effects model, for 61 (51.7%) out of 118 BoE-pairs, the 95% confidence interval (CI) excludes no effect. By pooling BoE from RCTs and cohort studies, the median I² was 48%, and the median contributed percentage weight of RCTs to the pooled estimates was 40%. The direction of effect between BoE from RCTs and pooled effect estimates was mainly concordant (79.7%). The integration of BoE from cohort studies modified the conclusion (by examining the 95% CI) from BoE of RCTs in 32 (27%) of the 118 BoE-pairs, but the direction of effect was mainly concordant (88%).

CONCLUSIONS

Our findings provide insights for the potential impact of pooling both BoE in systematic reviews. In medical research, it is often important to rely on both evidence of RCTs and cohort studies to get a whole picture of an investigated intervention-disease association. A decision for or against pooling different study designs should also always take into account, for example, PI/ECO similarity, risk of bias, coherence of effect estimates, and also the trustworthiness of the evidence. Overall, there is a need for more research on the influence of those issues on potential pooling.

Evaluating agreement between bodies of evidence from randomized controlled trials and cohort studies in medical research: a meta-epidemiological study

BACKGROUND

Randomized controlled trials (RCTs) and cohort studies are the most common study design types used to assess the treatment effects of medical interventions. To evaluate the agreement of effect estimates between bodies of evidence (BoE) from randomized controlled trials (RCTs) and cohort studies and to identify factors associated with disagreement.

METHODS

Systematic reviews were published in the 13 medical journals with the highest impact factor identified through a MEDLINE search. BoE-pairs from RCTs and cohort studies with the same medical research question were included. We rated the similarity of PI/ECO (Population, Intervention/Exposure, Comparison, Outcome) between BoE from RCTs and cohort studies. The agreement of effect estimates across BoE was analyzed by pooling ratio of ratios (RoR) for binary outcomes and difference of mean differences for continuous outcomes. We performed subgroup analyses to explore factors associated with disagreements.

RESULTS

One hundred twenty-nine BoE pairs from 64 systematic reviews were included. PI/ECO-similarity degree was moderate: two BoE pairs were rated as "more or less identical"; 90 were rated as "similar but not identical" and 37 as only "broadly similar". For binary outcomes, the pooled RoR was 1.04 (95% CI 0.97-1.11) with considerable statistical heterogeneity. For continuous outcomes, differences were small. In subgroup analyses, degree of PI/ECO-similarity, type of intervention, and type of outcome, the pooled RoR indicated that on average, differences between both BoE were small. Subgroup analysis by degree of PI/ECO-similarity revealed high statistical heterogeneity and wide prediction intervals across PI/ECO-dissimilar BoE pairs.

CONCLUSIONS

On average, the pooled effect estimates between RCTs and cohort studies did not differ. Statistical heterogeneity and wide prediction intervals were mainly driven by PI/ECO-dissimilarities (i.e., clinical heterogeneity) and cohort studies. The potential influence of risk of bias and certainty of the evidence on differences of effect estimates between RCTs and cohort studies needs to be explored in upcoming meta-epidemiological studies.

Cost-Effectiveness Analysis of Switching from Trivalent to Quadrivalent Seasonal Influenza Vaccine in Argentina

The burden of seasonal influenza disease in Argentina is considerable. The cost-effectiveness of trivalent (TIV) versus quadrivalent influenza vaccine (QIV) in Argentina was assessed. An age-stratified, static, decision-tree model compared the costs and benefits of vaccination for an average influenza season. Main outcomes included: numbers of influenza cases; general practitioner (GP) visits; complicated ambulatory cases; hospitalizations; deaths averted; and costs per quality-adjusted life years (QALYs) gained. Epidemiological data from Argentina for 2014–2019 were used to determine the proportion of A and B strain cases, and the frequency of mismatch between vaccine and circulating B strains. To manage uncertainty, one-way and probabilistic sensitivity analyses were performed. Switching from TIV to QIV would prevent 19,128 influenza cases, 16,164 GP visits, 2440 complicated ambulatory cases, 524 hospitalizations, and 82 deaths. Incremental cost–effectiveness ratios (ICERs) per QALY were 13,590 and 11,678 USD from the payer’s and societal perspectives, respectively. The greatest health benefits and direct medical cost savings would occur in ≥ 65-year-olds. One-way sensitivity analyses demonstrated the principal drivers of ICER to be vaccine acquisition costs, environmental B strain predominance, and B strain mismatch. Introducing QIV in Argentina would be beneficial and cost-effective relative to TIV, particularly in older adults.

A Reduced Dose Whole Virion Aluminum Adjuvanted Seasonal Influenza Vaccine Is Immunogenic, Safe, and Well Tolerated in Pediatric Patients

Background: Data suggest that pediatric patients might react differently to influenza vaccination, both in terms of immunity and side effects. We have recently shown that using a whole virion vaccine with aluminum phosphate adjuvants, reduced dose vaccines containing 6 µg of viral hemagglutinin (HA) per strain are immunogenic, and well tolerated in adult and elderly patients. Here we show the results of a multicenter clinical trial of pediatric patients, using reduced doses of a new, whole virion, aluminum phosphate adjuvanted vaccine (FluArt, Budapest, Hungary). Methods: A total of 120 healthy volunteers were included in two age groups (3–11 years, receiving 3 µg of HA per strain, and 12–18 years, receiving 6 µg of HA per strain). We used hemagglutination inhibition testing to assess immunogenicity, based on EMA and FDA licensing criteria, including post/pre-vaccination geometric mean titer ratios, seroconversion and seropositivity rates. Safety and tolerability were assessed using CHMP guidelines. Results: All subjects entered the study and were vaccinated (ITT population). All 120 subjects attended the control visit on Day 21 (PP population). All immunogenicity licensing criteria were met in both age groups for all three vaccine virus strains. No serious adverse events were detected and the vaccine was well tolerated by both age groups. Discussion: Using a whole virion vaccine and aluminum phosphate adjuvants, a reduction in the amount of the viral hemmaglutinin is possible while maintaining immunogenicity, safety and tolerability in pediatric and adolescent patients.

Early Induction of Cross-Reactive CD8+ T-Cell Responses in Tonsils After Live-Attenuated Influenza Vaccination in Children

BACKGROUND

Live-attenuated influenza vaccine (LAIV) was licensed for prophylaxis of children 2-17 years old in Europe in 2012 and is administered as a nasal spray. Live-attenuated influenza vaccine induces both mucosal and systemic antibodies and systemic T-cell responses. Tonsils are the lymph nodes serving the upper respiratory tract, acting as both induction and effector site for mucosal immunity.

METHODS

Here, we have studied the early tonsillar T-cell responses induced in children after LAIV. Thirty-nine children were immunized with trivalent LAIV (containing A/H1N1, A/H3N2, and B viruses) at days 3, 7, and 14 before tonsillectomy. Nonvaccinated controls were included for comparison. Tonsils and peripheral blood (pre- and postvaccination) were collected to study T-cell responses.

RESULTS

Tonsillar and systemic T-cell responses differed between influenza strains, and both were found against H3N2 and B viruses, whereas only systemic responses were observed against A/H1N1. A significant increase in cross-reactive tonsillar CD8+ T cells recognizing conserved epitopes from a broad range of seasonal and pandemic viruses occurred at day 14. Tonsillar T cells showed significant cytokine responses (Th1, Th2, and granulocyte-macrophage colony-stimulating factor).

CONCLUSIONS

Our findings support the use of LAIV in children to elicit broadly cross-reactive T cells, which are not induced by traditional inactivated influenza vaccines and may provide protection to novel virus strains.

Repeated exposure to an MF-59 adjuvanted quadrivalent subunit influenza vaccine (aQIV) in children: Results of two revaccination studies

BACKGROUND

Pediatric adjuvanted seasonal influenza vaccines induce higher immune responses and have the potential to confer better protection against influenza among young vaccine-naïve children. Limited data describe benefits and risks of repeated administration of adjuvanted influenza vaccines in children. Two revaccination studies assess the safety and immunogenicity of repeated exposure to an MF59-adjuvanted quadrivalent influenza vaccine (aQIV; Fluad®) compared to routine non-adjuvanted quadrivalent influenza vaccine (QIV).

METHODS

Children previously enrolled in the parent study, who received vaccination with aQIV or nonadjuvanted influenza vaccine (TIV or QIV), were recruited in Season 1 (n = 607) or Season 2 (n = 1601) of the extension trials. Season 1 participants remained in their original randomization groups (aQIV-aQIV or TIV-QIV); Season 2 subjects were re-randomized to either vaccine, resulting in four groups (aQIV-aQIV, aQIV-QIV, QIV-aQIV, or QIV-QIV). All subjects received a single-dose vaccination. Blood samples were taken for immunogenicity assessment prior to vaccination and 21 and 180 days after vaccination. Reactogenicity (Days 1-7) and safety were assessed in all subjects.

RESULTS

Hemagglutination inhibition (HI) geometric mean titer (GMT) ratios demonstrated superiority of aQIV revaccination over QIV revaccination for all strains in Season 1 and for A/H1N1, B/Yamagata, and B/Victoria in Season 2. Higher HI titers against heterologous influenza strains were observed after aQIV vaccination during both seasons. Mild to moderate severity and short duration reactogenicity was more common in the aQIV than QIV groups, but the overall safety profiles were similar to the parent study.

CONCLUSION

The safety and immunogenicity results from this study demonstrate benefit of aQIV for both priming and revaccination of children aged 12 months to 7 years.

Vaccine effectiveness of live attenuated and trivalent inactivated influenza vaccination in 2010/11 to 2015/16: the SIVE II record linkage study

BACKGROUND

There is good evidence of vaccine effectiveness in healthy individuals but less robust evidence for vaccine effectiveness in the populations targeted for influenza vaccination. The live attenuated influenza vaccine (LAIV) has recently been recommended for children in the UK. The trivalent influenza vaccine (TIV) is recommended for all people aged ≥ 65 years and for those aged < 65 years who are at an increased risk of complications from influenza infection (e.g. people with asthma).

OBJECTIVE

To examine the vaccine effectiveness of LAIV and TIV.

DESIGN

Cohort study and test-negative designs to estimate vaccine effectiveness. A self-case series study to ascertain adverse events associated with vaccination.

SETTING

A national linkage of patient-level general practice (GP) data from 230 Scottish GPs to the Scottish Immunisation & Recall Service, Health Protection Scotland virology database, admissions to Scottish hospitals and the Scottish death register.

PARTICIPANTS

A total of 1,250,000 people.

INTERVENTIONS

LAIV for 2- to 11-year-olds and TIV for older people (aged ≥ 65 years) and those aged < 65 years who are at risk of diseases, from 2010/11 to 2015/16.

MAIN OUTCOME MEASURES

The main outcome measures include vaccine effectiveness against laboratory-confirmed influenza using real-time reverse-transcription polymerase chain reaction (RT-PCR), influenza-related morbidity and mortality, and adverse events associated with vaccination.

RESULTS

Two-fifths (40%) of preschool-aged children and three-fifths (60%) of primary school-aged children registered in study practices were vaccinated. Uptake varied among groups [e.g. most affluent vs. most deprived in 2- to 4-year-olds, odds ratio 1.76, 95% confidence interval (CI) 1.70 to 1.82]. LAIV-adjusted vaccine effectiveness among children (aged 2-11 years) for preventing RT-PCR laboratory-confirmed influenza was 21% (95% CI -19% to 47%) in 2014/15 and 58% (95% CI 39% to 71%) in 2015/16. No significant adverse events were associated with LAIV. Among at-risk 18- to 64-year-olds, significant trivalent influenza vaccine effectiveness was found for four of the six seasons, with the highest vaccine effectiveness in 2010/11 (53%, 95% CI 21% to 72%). The seasons with non-significant vaccine effectiveness had low levels of circulating influenza virus (2011/12, 5%; 2013/14, 9%). Among those people aged ≥ 65 years, TIV effectiveness was positive in all six seasons, but in only one of the six seasons (2013/14) was significance achieved (57%, 95% CI 20% to 76%).

CONCLUSIONS

The study found that LAIV was safe and effective in decreasing RT-PCR-confirmed influenza in children. TIV was safe and significantly effective in most seasons for 18- to 64-year-olds, with positive vaccine effectiveness in most seasons for those people aged ≥ 65 years (although this was significant in only one season).

FUTURE WORK

The UK Joint Committee on Vaccination and Immunisation has recommended the use of adjuvanted injectable vaccine for those people aged ≥ 65 years from season 2018/19 onwards. A future study will be required to evaluate this vaccine.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN88072400.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 67. See the NIHR Journals Library website for further project information.

Influenza vaccination in the COVID-19 era

Influenza spreads globally annually with significant paediatric and adult attack rates and considerable morbidity, mortality and the exacerbation of extant chronic disease. In the northern and southern hemispheres, outbreaks occur mainly in the respective winter seasons. Influenza vaccination is available but only partially effective. In the absence of a vaccine, in winter, novel coronavirus COVID-19 will also circulate in parallel with seasonal influenza. Thus far it appears that with the current strains of these two viruses, the clinical outcome of co-infection is not significantly worse than infection with COVID-19 alone. However, several strains of influenza circulate, including strains still to come. Similarly, COVID-19 has several strains, with probably more to come. This paper discusses these issues and estimates ideal minimum influenza vaccination coverage based on an estimated influenza Basic Reproduction Number (R0) of 0.9-2.1 so as to obtain herd immunity or approach it. There is a strong argument for attempting near universal population coverage with the annual influenza vaccine leading up to next winter.

Public health and economic impact of switching from a trivalent to a quadrivalent inactivated influenza vaccine in Mexico

Most influenza vaccines in Mexico are trivalent, containing two influenza A strains and a single B strain. Quadrivalent influenza vaccines (QIVs) extend protection by including an additional B strain to cover both co-circulating B lineages. Here, we retrospectively estimated how a switch to QIV in Mexico would have impacted influenza-related health outcomes over the 2010/2011 to 2015/2016 influenza seasons, and prospectively estimated the budget impact of using QIV in Mexico's national immunization program from 2016/2017 to 2020/2021. For the retrospective estimation, we used an age-stratified static model incorporating Mexico-specific input parameters. For the prospective estimation, we used a budget impact model based on retrospective attack rates considering predicted future vaccination coverage. Between 2010/2011 and 2015/2016, a switch to QIV would have prevented 270,596 additional influenza cases, 102,000 general practitioner consultations, 140,062 days of absenteeism, 3,323 hospitalizations, and 312 deaths, saving Mex$214 million (US$10.8 million) in third-party payer costs. In the prospective analysis, a switch to QIV was estimated to prevent an additional 225,497 influenza cases, 85,000 general practitioner consultations, 116,718 days of absenteeism, 2,769 hospitalizations, and 260 deaths, saving Mex$178 million (US$9 million) in third-party payer costs over 5 years. Compared to the trivalent vaccine, the benefit and costs saved with QIV were sensitive to the distribution of influenza A vs. B cases and trivalent vaccine effectiveness against the mismatched B strain. These results suggest switching to QIV in Mexico would benefit healthcare providers and society by preventing influenza cases, morbidity, and deaths, and reducing associated use of medical resources.

Assessing direct and indirect effects of pediatric influenza vaccination in Germany by individual-based simulations

Children have a high burden of influenza and play a central role in spreading influenza. Routinely vaccinating children against influenza may, thus, not only reduce their disease burden, but also that of the general population, including the elderly who frequently suffer severe complications. Using the published individual-based tool 4Flu, we simulated how pediatric vaccination would change infection incidence in Germany. Transmission of four influenza strains was simulated in 100,000 individuals with German demography and contact structure. After initialization with the recorded trivalent influenza vaccination coverage for 20 years (1997-2016), all vaccinations were switched to quadrivalent influenza vaccine (QIV). Scenarios where vaccination coverage of children (0.5-17-year-old) was increased from the current value (4.3%) to a maximum of 10-60% were compared to baseline with unchanged coverage, averaging results of 1,000 pairs of simulations over a 20-year evaluation period (2017-2036). Pediatric vaccination coverage of 10-60% annually prevented 218-1,732 (6.3-50.5%) infections in children, 204-1,961 (2.9-28.2%) in young adults and 95-868 (3.1-28.9%) in the elderly in a population of 100,000 inhabitants; overall, 34.1% of infections in the total population (3.7 million infections per year in Germany) can be prevented if 60% of all children are vaccinated annually. 4.4-4.6 vaccinations were needed to prevent one infection among children; 1.7-1.8 were needed to prevent one in the population. Enhanced pediatric vaccination prevents many infections in children and even more in young adults and the elderly.

Characteristics of stakeholder involvement in systematic and rapid reviews: a methodological review in the area of health services research

OBJECTIVE

Engaging stakeholders in reviews is considered to generate more relevant evidence and to facilitate dissemination and use. As little is known about stakeholder involvement, we assessed the characteristics of their engagement in systematic and rapid reviews and the methodological quality of included studies. Stakeholders were people with a particular interest in the research topic.

DESIGN

Methodological review.

SEARCH STRATEGY

Four databases (Medline, Embase, Cochrane database of systematic reviews, databases of the University of York, Center for Reviews and Dissemination (CRD)) were searched based on an a priori protocol. Four types of reviews (Cochrane and non-Cochrane systematic reviews, rapid and CRD rapid reviews) were retrieved between January 2011 and October 2015, pooled by potential review type and duplicates excluded. Articles were randomly ordered and screened for inclusion and exclusion criteria until 30 reviews per group were reached. Their methodological quality was assessed using AMSTAR and stakeholder characteristics were collected.

RESULTS

In total, 57 822 deduplicated citations were detected with potential non-Cochrane systematic reviews being the biggest group (56 986 records). We found stakeholder involvement in 13% (4/30) of Cochrane, 20% (6/30) of non-Cochrane, 43% (13/30) of rapid and 93% (28/30) of CRD reviews. Overall, 33% (17/51) of the responding contact authors mentioned positive effects of stakeholder involvement. A conflict of interest statement remained unmentioned in 40% (12/30) of non-Cochrane and in 27% (8/30) of rapid reviews, but not in Cochrane or CRD reviews. At most, half of non-Cochrane and rapid reviews mentioned an a priori study protocol in contrast to all Cochrane reviews.

CONCLUSION

Stakeholder engagement was not general practice, except for CRD reviews, although it was more common in rapid reviews. Reporting factors, such as including an a priori study protocol and a conflict of interest statement should be considered in conjunction with involving stakeholders.

[Postvaccinal complications and management of suspected cases]

In all developed countries there is the possibility to protect oneself from vaccine-preventable diseases. However, not all individuals make use of this option. It is precisely in highly developed countries where a trend to vaccination hesitancy is noticeable, i. e. reluctance to get oneself or one's children vaccinated. The reasons why this is so are many, but the most important reason is the fear of postvaccinal complications, especially of those that imply sequelae or those with fatal outcomes.Whereas there are some proven associations between vaccination and adverse drug reaction, for example febrile seizures after the measles-mumps-rubella (MMR) vaccination, other hypotheses can be refuted, for example autism after the MMR vaccination. On one hand, this article gives an overview of known postvaccinal complications with indication of a causal association with vaccination and on the other hand addresses hypotheses of potential adverse drug reactions that have been refuted by pharmacoepidemiological studies.Only the scientific debate of these hypotheses, which are repeatedly discussed, especially on social media, can contribute to corroborating or refuting a potential causal association. If evidence for a causal association grows, e. g. intussusception, the relevant authorities (e.g. Paul Ehrlich Institute, European Medicines Agency) will take risk-minimizing measures. If studies and meta-analyses do not reveal any evidence of a causal association, a targeted information strategy will be required in order to prevent myths from circulating, vaccination coverages from declining, and infectious diseases from spreading.

A paediatric influenza update 100 years after the Skyros island Spanish flu outbreak

This year marks the 100th anniversary of the 1918 Spanish flu outbreak on the Greek Aegean Sea island of Skyros, which devastated its population in less than 30 days. According to Constantinos Faltaits's annals published in 1919, the influenza attack on the island of Skyros commenced acutely ‘like a thunderbolt’ on the 27th of October, 1918 and was exceptionally severe and fatal. At that time, the viral cause of the influenza had not been detected, while the total number of victims of the Spanish flu outbreak has been estimated to have surpassed 50 million, worldwide. Almost one century after this Aegean Sea island's tragedy, the ‘4th Workshop on Paediatric Virology’, organised on the 22nd of September, 2018 in Athens, Greece, was dedicated to the 100 years of the ‘Spanish’ flu pandemic. This review article highlights the plenary and key lectures presented at the workshop on the recent advances on the epidemiology, clinical management and prevention of influenza in childhood.

Novel Approaches for The Development of Live Attenuated Influenza Vaccines

Influenza virus still represents a considerable threat to global public health, despite the advances in the development and wide use of influenza vaccines. Vaccination with traditional inactivate influenza vaccines (IIV) or live-attenuated influenza vaccines (LAIV) remains the main strategy in the control of annual seasonal epidemics, but it does not offer protection against new influenza viruses with pandemic potential, those that have shifted. Moreover, the continual antigenic drift of seasonal circulating influenza viruses, causing an antigenic mismatch that requires yearly reformulation of seasonal influenza vaccines, seriously compromises vaccine efficacy. Therefore, the quick optimization of vaccine production for seasonal influenza and the development of new vaccine approaches for pandemic viruses is still a challenge for the prevention of influenza infections. Moreover, recent reports have questioned the effectiveness of the current LAIV because of limited protection, mainly against the influenza A virus (IAV) component of the vaccine. Although the reasons for the poor protection efficacy of the LAIV have not yet been elucidated, researchers are encouraged to develop new vaccination approaches that overcome the limitations that are associated with the current LAIV. The discovery and implementation of plasmid-based reverse genetics has been a key advance in the rapid generation of recombinant attenuated influenza viruses that can be used for the development of new and most effective LAIV. In this review, we provide an update regarding the progress that has been made during the last five years in the development of new LAIV and the innovative ways that are being explored as alternatives to the currently licensed LAIV. The safety, immunogenicity, and protection efficacy profile of these new LAIVs reveal their possible implementation in combating influenza infections. However, efforts by vaccine companies and government agencies will be needed for controlled testing and approving, respectively, these new vaccine methodologies for the control of influenza infections.

Prioritization of risk groups for influenza vaccination in resource limited settings - A case study from South Africa

BACKGROUND

Due to competing health priorities, low- and middle-income countries (LMIC) may need to prioritize between different influenza vaccine risk groups. Risk group prioritization may differ in LMIC based upon programmatic feasibility, country-specific prevalence of risk conditions and influenza-associated morbidity and mortality.

METHODS

In South Africa, we collected local disease burden data (both published and unpublished) and published vaccine efficacy data in risk groups and healthy adults. We used these data to aid policy makers with risk group prioritization for influenza vaccination. We used the following formula to assess potential vaccine averted disease in each risk group: rate of influenza-associated hospitalization (or death) per 100,000 population * influenza vaccine efficacy (VE). We further estimated the cost per hospital day averted and the cost per year of life saved by influenza vaccination.

RESULTS

Pregnant women, HIV-infected adults, and adults and children with tuberculosis disease had among the highest estimates of hospitalizations averted per 100,000 vaccinated and adults aged 65 years and older had the highest estimated deaths averted per 100,000 vaccinated. However, when assessing both the cost per hospital day averted (range: USD148-1,344) and the cost per year of life saved (range: USD112-1,230); adults and children with TB disease, HIV-infected adults and pregnant women had the lowest cost per outcome averted.

DISCUSSION

An assessment of the potential disease outcomes averted and associated costs may aid policymakers in risk group prioritization for influenza vaccination.

Cost Effectiveness of Quadrivalent Influenza Vaccines Compared with Trivalent Influenza Vaccines in Young Children and Older Adults in Korea

INTRODUCTION

Trivalent influenza vaccines (TIVs) are currently reimbursed for subjects aged ≥ 65 years and children between 6 and 59 months of age under a national immunization program in South Korea. Quadrivalent influenza vaccines (QIVs) are expected to address the potential problem of influenza B-lineage mismatch for TIVs.

OBJECTIVE

The objective of this analysis was to compare the cost effectiveness of QIV versus TIV in children aged 6-59 months and older adults ≥ 65 years of age in South Korea.

METHODS

A 1-year static population model was employed to compare the costs and outcomes of a QIV vaccination program compared with TIV in children aged 6-59 months and older adults ≥ 65 years of age in South Korea. Influenza-related parameters (probabilities, health resource use, and costs) were derived from an analysis of the National Health Insurance System claims database between 2010 and 2013 under a broad and narrow set of International Classification of Diseases, Tenth Revision (ICD-10) codes used to identify influenza. Other inputs were extracted from published literature. Incremental cost-effectiveness ratios (2016 South Korean Won [KRW] per quality-adjusted life-year [QALY] gained) were estimated using a 'limited' societal perspective as per the Korean pharmacoeconomic guidelines. QALYs lost due to premature mortality were discounted at 5% annually.

RESULTS

For both age groups combined, under the narrow definition of influenza, QIV is expected to prevent nearly 16,000 (2923 in children and 13,011 in older adults) medically attended influenza cases, nearly 8000 (672 in children, 7048 in older adults) cases of complications, and over 230 (0 in children, 238 in older adults) deaths annually compared with TIV. The impact of using QIV versus TIV in this setting translates into savings of KRW 24 billion (KRW 0.6 billion in children, KRW 23.4 billion in older adults) in annual medical costs, and over 2100 (18 in children, 2084 in older adults) QALYs. Under the broad definition, the corresponding results are over 190,000 (50,697 in children, 140,644 in older adults) influenza cases, over 37,000 (12,623 in children, 24,526 in older adults) complications, 270 deaths (0 in children, 270 in older adults), KRW 94.22 billion (KRW 16 billion in children, KRW 78.2 billion in older adults), and over 3500 QALYs saved (316 in children, 3260 in older adults).

CONCLUSION

The use of QIV over TIV was estimated to not be cost effective in children 6-59 months of age, but cost saving in older adults, using the narrow definition of influenza; however, QIV use was cost saving in both age groups using the broad definition. QIV is expected to yield more benefits in older adults ≥ 65 years of age than in children aged 6-59 months due to higher influenza-related mortality and costs among the older adults. Further analyses considering the indirect effects of influenza vaccination in children are required.

DNA vaccine priming for seasonal influenza vaccine in children and adolescents 6 to 17 years of age: A phase 1 randomized clinical trial

BACKGROUND

Children are susceptible to severe influenza infections and facilitate community transmission. One potential strategy to improve vaccine immunogenicity in children against seasonal influenza involves a trivalent hemagglutinin DNA prime-trivalent inactivated influenza vaccine (IIV3) boost regimen.

METHODS

Sites enrolled adolescents, followed by younger children, to receive DNA prime (1 mg or 4 mg) intramuscularly by needle-free jet injector (Biojector), followed by split virus 2012/13 seasonal IIV3 boost by needle and syringe approximately 18 weeks later. A comparator group received IIV3 prime and boost at similar intervals. Primary study objectives included evaluation of the safety and tolerability of the vaccine regimens, with secondary objectives of measuring antibody responses at four weeks post boost by hemagglutination inhibition (HAI) and neutralization assays.

RESULTS

Seventy-five children ≥6 to ≤17 years old enrolled. Local reactogenicity was higher after DNA prime compared to IIV3 prime (p<0.001 for pain/tenderness, redness, or swelling), but symptoms were mild to moderate in severity. Systemic reactogenicity was similar between vaccines. Overall, antibody responses were similar among groups, although HAI antibodies revealed a trend towards higher responses following 4 mg DNA-IIV3 compared to IIV3-IIV3. The fold increase of HAI antibodies to A/California/07/2009 [A(H1N1)pdm09] was significantly greater following 4 mg DNA-IIV3 (10.12 fold, 5.60-18.27 95%CI) compared to IIV3-IIV3 (3.86 fold, 2.32-6.44 95%CI). Similar neutralizing titers were observed between regimens, with a trend towards increased response frequencies in 4 mg DNA-IIV3. However, significant differences in fold increase, reported as geometric mean fold ratios, were detected against the H1N1 viruses within the neutralization panel: A/New Caledonia/20/1999 (1.41 fold, 1.10-1.81 95%CI) and A/South Carolina/1/1918 (1.55 fold, 1.27-1.89 95%CI).

CONCLUSIONS

In this first pediatric DNA vaccine study conducted in the U.S., the DNA prime-IIV3 boost regimen was safe and well tolerated. In children, the 4 mg DNA-IIV3 regimen resulted in antibody responses comparable to the IIV3-IIV3 regimen.

Infectious illness prevention and control methods and their effectiveness in non-health workplaces: an integrated literature review

BACKGROUND

Infectious illness in the workplace places a substantial cost burden on employers due to productivity losses from employee absenteeism and presenteeism.

AIM

Given the clear impacts of infectious illness on workplaces, this review aimed to investigate the international literature on the effectiveness and cost-benefit of the strategies non-healthcare workplaces use to prevent and control infectious illnesses in these workplaces.

METHODS

MEDLINE, CINAHL Plus with Fulltext and Business Source Complete were searched concurrently using EBSCO Host 1995-2016.

FINDINGS

Infection prevention and control strategies to reduce workplace infectious illness and absenteeism evaluated in the literature include influenza vaccination programs, use of alcohol-based hand sanitiser and paid sick days. While the reported studies have various methodological flaws, there is good evidence of the effectiveness of influenza vaccination in preventing workplace infectious illness and absences and moderate evidence to support hand hygiene programs.

DISCUSSION

Some studies used more than one intervention concurrently, making it difficult to determine the relative benefit of each individual strategy. Workplace strategies to prevent and control infectious illness transmission may reduce costs and productivity losses experienced by businesses and organisations related to infectious illness absenteeism and presenteeism.

A qualitative analysis of the beliefs of Japanese anti-influenza vaccination website authors

Background

Influenza vaccine coverage among the Japanese population is less than optimal. Anti-vaccination sentiment exists worldwide, and Japan is no exception. Anti-influenza vaccination activists argue on the internet that influenza vaccine has little or no efficacy and a high risk of side effects, and they warn that people should forgo vaccination. We conducted a qualitative analysis to explore beliefs underlying the messages of anti-influenza vaccination websites, by focusing on the perceived value these beliefs provide to those who hold them.

Methods

We conducted online searches in January 2017 using two major Japanese search engines (Google Japan and Yahoo! Japan). Targeted websites were classified as “pro”, “anti”, or “neutral” depending on their claims. We applied a dual analytic approach—inductive thematic analysis and deductive interpretative analysis—to textual data of the anti websites.

Results

Of the 113 anti websites, we identified two themes that correspond to beliefs: it is necessary to 1) protect others against risks and exploitation related to influenza vaccination, and 2) educate others about hidden truths and self-determination. Authors of anti websites ascribed two values (people's “safety” and one's own “self-esteem”) to their beliefs.

Discussion

Website authors may engage in anti-vaccination activities because they want to feel they are virtuous, saving people from harm caused by vaccination, and to boost their self-esteem, thinking “I am enlightening uninformed people.” The anti-vaccination beliefs of website authors were considered to be strong. In promoting vaccination, it would be better not to target outright vaccine refusers, such as the authors of anti-vaccination websites; it is preferable to target vaccine-hesitant people who are more amenable to changing their attitudes toward vaccination. We discuss possible means of promoting vaccination in that target population.

Neonatal Immunity, Respiratory Virus Infections, and the Development of Asthma

Infants are exposed to a wide range of potential pathogens in the first months of life. Although maternal antibodies acquired transplacentally protect full-term neonates from many systemic pathogens, infections at mucosal surfaces still occur with great frequency, causing significant morbidity and mortality. At least part of this elevated risk is attributable to the neonatal immune system that tends to favor T regulatory and Th2 type responses when microbes are first encountered. Early-life infection with respiratory viruses is of particular interest because such exposures can disrupt normal lung development and increase the risk of chronic respiratory conditions, such as asthma. The immunologic mechanisms that underlie neonatal host-virus interactions that contribute to the subsequent development of asthma have not yet been fully defined. The goals of this review are (1) to outline the differences between the neonatal and adult immune systems and (2) to present murine and human data that support the hypothesis that early-life interactions between the immune system and respiratory viruses can create a lung environment conducive to the development of asthma.

Trends of influenza B during the 2010-2016 seasons in 2 regions of north and south Italy: The impact of the vaccine mismatch on influenza immunisation strategy

Influenza A and B viruses are responsible for respiratory infections, representing globally seasonal threats to human health. The 2 viral types often co-circulate and influenza B plays an important role in the spread of infection. A 6-year retrospective surveillance study was conducted between 2010 and 2016 in 2 large administrative regions of Italy, located in the north (Liguria) and in the south (Sicily) of the country, to describe the burden and epidemiology of both B/Victoria and B/Yamagata lineages in different healthcare settings. Influenza B viruses were detected in 5 of 6 seasonal outbreaks, exceeding influenza A during the season 2012-2013. Most of influenza B infections were found in children aged ≤ 14 y and significant differences were observed in the age-groups infected by the different lineages. B/Victoria strains prevailed in younger population than B/Yamagata, but also were more frequently found in the community setting. Conversely, B/Yamagata viruses were prevalent among hospitalized cases suggesting their potential role in the development of more severe disease. The relative proportions of viral lineages varied from year to year, resulting in different lineage-level mismatch for the B component of trivalent influenza vaccine. Our findings confirmed the need for continuous virological surveillance of seasonal epidemics and bring attention to the adoption of universal influenza immunization program in the childhood. The use of tetravalent vaccine formulations may be useful to improve the prevention and control of the influenza burden in general population.

Immune responses after live attenuated influenza vaccination

Since 2003 (US) and 2012 (Europe) the live attenuated influenza vaccine (LAIV) has been used as an alternative to the traditional inactivated influenza vaccines (IIV). The immune responses elicted by LAIV mimic natural infection and have been found to provide broader clinical protection in children compared to the IIVs. However, our knowledge of the detailed immunological mechanisims induced by LAIV remain to be fully elucidated, and despite 14 years on the global market, there exists no correlate of protection. Recently, matters are further complicated by differing efficacy data from the US and Europe which are not understood. Better understanding of the immune responses after LAIV may aid in achieving the ultimate goal of a future "universal influenza vaccine". In this review we aim to cover the current understanding of the immune responses induced after LAIV.

Vaccines for preventing influenza in healthy children

BACKGROUND

The consequences of influenza in children and adults are mainly absenteeism from school and work. However, the risk of complications is greatest in children and people over 65 years of age. This is an update of a review published in 2011. Future updates of this review will be made only when new trials or vaccines become available. Observational data included in previous versions of the review have been retained for historical reasons but have not been updated because of their lack of influence on the review conclusions.

OBJECTIVES

To assess the effects (efficacy, effectiveness, and harm) of vaccines against influenza in healthy children.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library 2016, Issue 12), which includes the Cochrane Acute Respiratory Infections Group Specialised Register, MEDLINE (1966 to 31 December 2016), Embase (1974 to 31 December 2016), WHO International Clinical Trials Registry Platform (ICTRP; 1 July 2017), and ClinicalTrials.gov (1 July 2017).

SELECTION CRITERIA

Randomised controlled trials comparing influenza vaccines with placebo or no intervention in naturally occurring influenza in healthy children under 16 years. Previous versions of this review included 19 cohort and 11 case-control studies. We are no longer updating the searches for these study designs but have retained the observational studies for historical purposes.

DATA COLLECTION AND ANALYSIS

Review authors independently assessed risk of bias and extracted data. We used GRADE to rate the certainty of evidence for the key outcomes of influenza, influenza-like illness (ILI), complications (hospitalisation, ear infection), and adverse events. Due to variation in control group risks for influenza and ILI, absolute effects are reported as the median control group risk, and numbers needed to vaccinate (NNVs) are reported accordingly. For other outcomes aggregate control group risks are used.

MAIN RESULTS

We included 41 clinical trials (> 200,000 children). Most of the studies were conducted in children over the age of two and compared live attenuated or inactivated vaccines with placebo or no vaccine. Studies were conducted over single influenza seasons in the USA, Western Europe, Russia, and Bangladesh between 1984 and 2013. Restricting analyses to studies at low risk of bias showed that influenza and otitis media were the only outcomes where the impact of bias was negligible. Variability in study design and reporting impeded meta-analysis of harms outcomes.Live attenuated vaccinesCompared with placebo or do nothing, live attenuated influenza vaccines probably reduce the risk of influenza infection in children aged 3 to 16 years from 18% to 4% (risk ratio (RR) 0.22, 95% confidence interval (CI) 0.11 to 0.41; 7718 children; moderate-certainty evidence), and they may reduce ILI by a smaller degree, from 17% to 12% (RR 0.69, 95% CI 0.60 to 0.80; 124,606 children; low-certainty evidence). Seven children would need to be vaccinated to prevent one case of influenza, and 20 children would need to be vaccinated to prevent one child experiencing an ILI. Acute otitis media is probably similar following vaccine or placebo during seasonal influenza, but this result comes from a single study with particularly high rates of acute otitis media (RR 0.98, 95% CI 0.95 to 1.01; moderate-certainty evidence). There was insufficient information available to determine the effect of vaccines on school absenteeism due to very low-certainty evidence from one study. Vaccinating children may lead to fewer parents taking time off work, although the CI includes no effect (RR 0.69, 95% CI 0.46 to 1.03; low-certainty evidence). Data on the most serious consequences of influenza complications leading to hospitalisation were not available. Data from four studies measuring fever following vaccination varied considerably, from 0.16% to 15% in children who had live vaccines, while in the placebo groups the proportions ranged from 0.71% to 22% (very low-certainty evidence). Data on nausea were not reported.Inactivated vaccinesCompared with placebo or no vaccination, inactivated vaccines reduce the risk of influenza in children aged 2 to 16 years from 30% to 11% (RR 0.36, 95% CI 0.28 to 0.48; 1628 children; high-certainty evidence), and they probably reduce ILI from 28% to 20% (RR 0.72, 95% CI 0.65 to 0.79; 19,044 children; moderate-certainty evidence). Five children would need to be vaccinated to prevent one case of influenza, and 12 children would need to be vaccinated to avoid one case of ILI. The risk of otitis media is probably similar between vaccinated children and unvaccinated children (31% versus 27%), although the CI does not exclude a meaningful increase in otitis media following vaccination (RR 1.15, 95% CI 0.95 to 1.40; 884 participants; moderate-certainty evidence). There was insufficient information available to determine the effect of vaccines on school absenteeism due to very low-certainty evidence from one study. We identified no data on parental working time lost, hospitalisation, fever, or nausea.We found limited evidence on secondary cases, requirement for treatment of lower respiratory tract disease, and drug prescriptions. One brand of monovalent pandemic vaccine was associated with a sudden loss of muscle tone triggered by the experience of an intense emotion (cataplexy) and a sleep disorder (narcolepsy) in children. Evidence of serious harms (such as febrile fits) was sparse.

AUTHORS' CONCLUSIONS

In children aged between 3 and 16 years, live influenza vaccines probably reduce influenza (moderate-certainty evidence) and may reduce ILI (low-certainty evidence) over a single influenza season. In this population inactivated vaccines also reduce influenza (high-certainty evidence) and may reduce ILI (low-certainty evidence). For both vaccine types, the absolute reduction in influenza and ILI varied considerably across the study populations, making it difficult to predict how these findings translate to different settings. We found very few randomised controlled trials in children under two years of age. Adverse event data were not well described in the available studies. Standardised approaches to the definition, ascertainment, and reporting of adverse events are needed. Identification of all global cases of potential harms is beyond the scope of this review.

Vaccines for preventing influenza in healthy adults

BACKGROUND

The consequences of influenza in adults are mainly time off work. Vaccination of pregnant women is recommended internationally. This is an update of a review published in 2014. Future updates of this review will be made only when new trials or vaccines become available. Observational data included in previous versions of the review have been retained for historical reasons but have not been updated due to their lack of influence on the review conclusions.

OBJECTIVES

To assess the effects (efficacy, effectiveness, and harm) of vaccines against influenza in healthy adults, including pregnant women.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 12), MEDLINE (January 1966 to 31 December 2016), Embase (1990 to 31 December 2016), the WHO International Clinical Trials Registry Platform (ICTRP; 1 July 2017), and ClinicalTrials.gov (1 July 2017), as well as checking the bibliographies of retrieved articles.

SELECTION CRITERIA

Randomised controlled trials (RCTs) or quasi-RCTs comparing influenza vaccines with placebo or no intervention in naturally occurring influenza in healthy individuals aged 16 to 65 years. Previous versions of this review included observational comparative studies assessing serious and rare harms cohort and case-control studies. Due to the uncertain quality of observational (i.e. non-randomised) studies and their lack of influence on the review conclusions, we decided to update only randomised evidence. The searches for observational comparative studies are no longer updated.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trial quality and extracted data. We rated certainty of evidence for key outcomes (influenza, influenza-like illness (ILI), hospitalisation, and adverse effects) using GRADE.

MAIN RESULTS

We included 52 clinical trials of over 80,000 people assessing the safety and effectiveness of influenza vaccines. We have presented findings from 25 studies comparing inactivated parenteral influenza vaccine against placebo or do-nothing control groups as the most relevant to decision-making. The studies were conducted over single influenza seasons in North America, South America, and Europe between 1969 and 2009. We did not consider studies at high risk of bias to influence the results of our outcomes except for hospitalisation.Inactivated influenza vaccines probably reduce influenza in healthy adults from 2.3% without vaccination to 0.9% (risk ratio (RR) 0.41, 95% confidence interval (CI) 0.36 to 0.47; 71,221 participants; moderate-certainty evidence), and they probably reduce ILI from 21.5% to 18.1% (RR 0.84, 95% CI 0.75 to 0.95; 25,795 participants; moderate-certainty evidence; 71 healthy adults need to be vaccinated to prevent one of them experiencing influenza, and 29 healthy adults need to be vaccinated to prevent one of them experiencing an ILI). The difference between the two number needed to vaccinate (NNV) values depends on the different incidence of ILI and confirmed influenza among the study populations. Vaccination may lead to a small reduction in the risk of hospitalisation in healthy adults, from 14.7% to 14.1%, but the CI is wide and does not rule out a large benefit (RR 0.96, 95% CI 0.85 to 1.08; 11,924 participants; low-certainty evidence). Vaccines may lead to little or no small reduction in days off work (-0.04 days, 95% CI -0.14 days to 0.06; low-certainty evidence). Inactivated vaccines cause an increase in fever from 1.5% to 2.3%.We identified one RCT and one controlled clinical trial assessing the effects of vaccination in pregnant women. The efficacy of inactivated vaccine containing pH1N1 against influenza was 50% (95% CI 14% to 71%) in mothers (NNV 55), and 49% (95% CI 12% to 70%) in infants up to 24 weeks (NNV 56). No data were available on efficacy against seasonal influenza during pregnancy. Evidence from observational studies showed effectiveness of influenza vaccines against ILI in pregnant women to be 24% (95% CI 11% to 36%, NNV 94), and against influenza in newborns from vaccinated women to be 41% (95% CI 6% to 63%, NNV 27).Live aerosol vaccines have an overall effectiveness corresponding to an NNV of 46. The performance of one- or two-dose whole-virion 1968 to 1969 pandemic vaccines was higher (NNV 16) against ILI and (NNV 35) against influenza. There was limited impact on hospitalisations in the 1968 to 1969 pandemic (NNV 94). The administration of both seasonal and 2009 pandemic vaccines during pregnancy had no significant effect on abortion or neonatal death, but this was based on observational data sets.

AUTHORS' CONCLUSIONS

Healthy adults who receive inactivated parenteral influenza vaccine rather than no vaccine probably experience less influenza, from just over 2% to just under 1% (moderate-certainty evidence). They also probably experience less ILI following vaccination, but the degree of benefit when expressed in absolute terms varied across different settings. Variation in protection against ILI may be due in part to inconsistent symptom classification. Certainty of evidence for the small reductions in hospitalisations and time off work is low. Protection against influenza and ILI in mothers and newborns was smaller than the effects seen in other populations considered in this review.Vaccines increase the risk of a number of adverse events, including a small increase in fever, but rates of nausea and vomiting are uncertain. The protective effect of vaccination in pregnant women and newborns is also very modest. We did not find any evidence of an association between influenza vaccination and serious adverse events in the comparative studies considered in this review. Fifteen included RCTs were industry funded (29%).

Vaccines for preventing influenza in the elderly

BACKGROUND

The consequences of influenza in the elderly (those age 65 years or older) are complications, hospitalisations, and death. The primary goal of influenza vaccination in the elderly is to reduce the risk of death among people who are most vulnerable. This is an update of a review published in 2010. Future updates of this review will be made only when new trials or vaccines become available. Observational data included in previous versions of the review have been retained for historical reasons but have not been updated because of their lack of influence on the review conclusions.

OBJECTIVES

To assess the effects (efficacy, effectiveness, and harm) of vaccines against influenza in the elderly.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library 2016, Issue 11), which includes the Cochrane Acute Respiratory Infections Group's Specialised Register; MEDLINE (1966 to 31 December 2016); Embase (1974 to 31 December 2016); Web of Science (1974 to 31 December 2016); CINAHL (1981 to 31 December 2016); LILACS (1982 to 31 December 2016); WHO International Clinical Trials Registry Platform (ICTRP; 1 July 2017); and ClinicalTrials.gov (1 July 2017).

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs assessing efficacy against influenza (laboratory-confirmed cases) or effectiveness against influenza-like illness (ILI) or safety. We considered any influenza vaccine given independently, in any dose, preparation, or time schedule, compared with placebo or with no intervention. Previous versions of this review included 67 cohort and case-control studies. The searches for these trial designs are no longer updated.

DATA COLLECTION AND ANALYSIS

Review authors independently assessed risk of bias and extracted data. We rated the certainty of evidence with GRADE for the key outcomes of influenza, ILI, complications (hospitalisation, pneumonia), and adverse events. We have presented aggregate control group risks to illustrate the effect in absolute terms. We used them as the basis for calculating the number needed to vaccinate to prevent one case of each event for influenza and ILI outcomes.

MAIN RESULTS

We identified eight RCTs (over 5000 participants), of which four assessed harms. The studies were conducted in community and residential care settings in Europe and the USA between 1965 and 2000. Risk of bias reduced our certainty in the findings for influenza and ILI, but not for other outcomes.Older adults receiving the influenza vaccine may experience less influenza over a single season compared with placebo, from 6% to 2.4% (risk ratio (RR) 0.42, 95% confidence interval (CI) 0.27 to 0.66; low-certainty evidence). We rated the evidence as low certainty due to uncertainty over how influenza was diagnosed. Older adults probably experience less ILI compared with those who do not receive a vaccination over the course of a single influenza season (3.5% versus 6%; RR 0.59, 95% CI 0.47 to 0.73; moderate-certainty evidence). These results indicate that 30 people would need to be vaccinated to prevent one person experiencing influenza, and 42 would need to be vaccinated to prevent one person having an ILI.The study providing data for mortality and pneumonia was underpowered to detect differences in these outcomes. There were 3 deaths from 522 participants in the vaccination arm and 1 death from 177 participants in the placebo arm, providing very low-certainty evidence for the effect on mortality (RR 1.02, 95% CI 0.11 to 9.72). No cases of pneumonia occurred in one study that reported this outcome (very low-certainty evidence). No data on hospitalisations were reported. Confidence intervaIs around the effect of vaccines on fever and nausea were wide, and we do not have enough information about these harms in older people (fever: 1.6% with placebo compared with 2.5% after vaccination (RR 1.57, 0.92 to 2.71; moderate-certainty evidence)); nausea (2.4% with placebo compared with 4.2% after vaccination (RR 1.75, 95% CI 0.74 to 4.12; low-certainty evidence)).

AUTHORS' CONCLUSIONS

Older adults receiving the influenza vaccine may have a lower risk of influenza (from 6% to 2.4%), and probably have a lower risk of ILI compared with those who do not receive a vaccination over the course of a single influenza season (from 6% to 3.5%). We are uncertain how big a difference these vaccines will make across different seasons. Very few deaths occurred, and no data on hospitalisation were reported. No cases of pneumonia occurred in one study that reported this outcome. We do not have enough information to assess harms relating to fever and nausea in this population.The evidence for a lower risk of influenza and ILI with vaccination is limited by biases in the design or conduct of the studies. Lack of detail regarding the methods used to confirm the diagnosis of influenza limits the applicability of this result. The available evidence relating to complications is of poor quality, insufficient, or old and provides no clear guidance for public health regarding the safety, efficacy, or effectiveness of influenza vaccines for people aged 65 years or older. Society should invest in research on a new generation of influenza vaccines for the elderly.

MicroRNA-Based Attenuation of Influenza Virus across Susceptible Hosts

Influenza A virus drives significant morbidity and mortality in humans and livestock. Annual circulation of the virus in livestock and waterfowl contributes to severe economic disruption and increases the risk of zoonotic transmission of novel strains into the human population, where there is no preexisting immunity. Seasonal vaccinations in humans help prevent infection and can reduce symptoms when infection does occur. However, current vaccination regimens available for livestock are limited in part due to safety concerns regarding reassortment/recombination with circulating strains. Therefore, inactivated vaccines are used instead of the more immunostimulatory live attenuated vaccines. MicroRNAs (miRNAs) have been used previously to generate attenuated influenza A viruses for use as a vaccine. Here, we systematically targeted individual influenza gene mRNAs using the same miRNA to determine the segment(s) that yields maximal attenuation potential. This analysis demonstrated that targeting of NP mRNA most efficiently ablates replication. We further increased the plasticity of miRNA-mediated attenuation of influenza A virus by exploiting a miRNA, miR-21, that is ubiquitously expressed across influenza-susceptible hosts. In order to construct this targeted virus, we used CRISPR/Cas9 to eliminate the universally expressed miR-21 from MDCK cells. miR-21-targeted viruses were attenuated in human, mouse, canine, and avian cells and drove protective immunity in mice. This strategy has the potential to enhance the safety of live attenuated vaccines in humans and zoonotic reservoirs.IMPORTANCE Influenza A virus circulates annually in both avian and human populations, causing significant morbidity, mortality, and economic burden. High incidence of zoonotic infections greatly increases the potential for transmission to humans, where no preexisting immunity or vaccine exists. There is a critical need for new vaccine strategies to combat emerging influenza outbreaks. MicroRNAs were used previously to attenuate influenza A viruses. We propose the development of a novel platform to produce live attenuated vaccines that are highly customizable, efficacious across a broad species range, and exhibit enhanced safety over traditional vaccination methods. This strategy exploits a microRNA that is expressed abundantly in influenza virus-susceptible hosts. By eliminating this ubiquitous microRNA from a cell line, targeted viruses that are attenuated across susceptible strains can be generated. This approach greatly increases the plasticity of the microRNA targeting approach and enhances vaccine safety.

Influenza immunization policies: Which could be the main reasons for differences among countries?

Despite the availability of effective prophylactic and therapeutic measures, influenza remains one of the most important infectious disease threats to the human population. Every year, seasonal influenza epidemics infect up to 30% of the population; a relevant portion of the ill are hospitalized, and more than a marginal number die. In an attempt to reduce the medical, social and economic burden of influenza, vaccines are recommended by many health authorities worldwide. However, not all countries have a national program for influenza immunization. The main aim of this paper is to list the differences among influenza immunization policies of various countries, highlighting the most important scientific reasons that may have led health authorities to make different decisions. The manuscript highlights that national influenza immunization policies can vary significantly from country to country. These differences arise from insufficient evidence of the relevance of influenza infection from a clinical, social and economic point of view. The lack of precise data on the true frequency and clinical relevance of influenza infection makes it nearly impossible to establish the economic burden of influenza. Moreover, it remains very difficult to evaluate the efficacy of the different influenza vaccines and whether their use is cost-effective considering the various types of people receiving them and the indirect advantages. Disparities among countries will be overcome only when more reliable data regarding all these aspects of influenza infection, particularly those related to the true impact of the disease, are precisely defined.

AS03- and MF59-Adjuvanted Influenza Vaccines in Children

Influenza is a major cause of respiratory disease leading to hospitalization in young children. However, seasonal trivalent influenza vaccines (TIVs) have been shown to be ineffective and poorly immunogenic in this population. The development of live-attenuated influenza vaccines and adjuvanted vaccines are important advances in the prevention of influenza in young children. The oil-in-water emulsions MF59 and adjuvant systems 03 (AS03) have been used as adjuvants in both seasonal adjuvanted trivalent influenza vaccines (ATIVs) and pandemic monovalent influenza vaccines. Compared with non-adjuvanted vaccine responses, these vaccines induce a more robust and persistent antibody response for both homologous and heterologous influenza strains in infants and young children. Evidence of a significant improvement in vaccine efficacy with these adjuvanted vaccines resulted in the use of the monovalent (A/H1N1) AS03-adjuvanted vaccine in children in the 2009 influenza pandemic and the licensure of the seasonal MF59 ATIV for children aged 6 months to 2 years in Canada. The mechanism of action of MF59 and AS03 remains unclear. Adjuvants such as MF59 induce proinflammatory cytokines and chemokines, including CXCL10, but independently of type-1 interferon. This proinflammatory response is associated with improved recruitment, activation and maturation of antigen presenting cells at the injection site. In young children MF59 ATIV produced more homogenous and robust transcriptional responses, more similar to adult-like patterns, than did TIV. Early gene signatures characteristic of the innate immune response, which correlated with antibody titers were also identified. Differences were detected when comparing child and adult responses including opposite trends in gene set enrichment at day 3 postvaccination and, unlike adult data, a lack of correlation between magnitude of plasmablast response at day 7 and antibody titers at day 28 in children. These insights show the utility of novel approaches in understanding new adjuvants and their importance for developing improved influenza vaccines for children.

Influenza Vaccination Strategies Should Target Children

Strategies to increase influenza vaccination rates have typically targeted healthcare professionals (HCPs) and individuals in various high-risk groups such as the elderly. We argue that they should (instead or as well) focus on increasing vaccination rates in children. Because children suffer higher influenza incidence rates than any other demographic group, and are major drivers of seasonal influenza epidemics, we argue that influenza vaccination strategies that serve to increase uptake rates in children are likely to be more effective in reducing influenza-related morbidity and mortality than those targeting HCPs or the elderly. This is true even though influenza-related morbidity and mortality amongst children are low, except in the very young. Further, we argue that there are no decisive reasons to suppose that children-focused strategies are less ethically acceptable than elderly or HCP-focused strategies.

Advances in Vaccines to Prevent Viral Respiratory Illnesses in Children

Childhood vaccination has played a critical role in the reduction of morbidity and mortality from communicable diseases, including specific respiratory pathogens. Acute lower respiratory infection (ALRI) of both bacterial and viral aetiology continues to impact global child health. Key bacterial pathogens including Streptococcus pneumoniae and Haemophilus influenza type b are specifically targeted with current vaccination programmes, while at present there are less effective strategies for the prevention of viral disease. Influenza vaccines, including both live attenuated intranasal vaccines and inactivated influenza vaccines, are limited by seasonal strain variation and unsustained immunity. Research into the development of a universal influenza vaccine is ongoing; potential targets are the conserved regions of the virus such as the M2e antigen and hemagglutinin stalk. Respiratory syncytial virus (RSV) and parainfluenza virus 3 (PIV3) are the viral pathogens most commonly causing ALRI in children, particularly the infant population. Currently, no vaccine exists for either virus. Over the last decade, promising advances have been made. Protection of neonates via maternal RSV immunisation is being assessed in a phase III clinical trial, with many other candidates for RSV and PIV3 at less advanced stages of development.

Vaccine effectiveness against laboratory-confirmed influenza hospitalizations among young children during the 2010-11 to 2013-14 influenza seasons in Ontario, Canada

Uncertainty remains regarding the magnitude of effectiveness of influenza vaccines for preventing serious outcomes, especially among young children. We estimated vaccine effectiveness (VE) against laboratory-confirmed influenza hospitalizations among children aged 6-59 months. We used the test-negative design in hospitalized children in Ontario, Canada during the 2010-11 to 2013-14 influenza seasons. We used logistic regression models adjusted for age, season, and time within season to calculate VE estimates by vaccination status (full vs. partial), age group, and influenza season. We also assessed VE incorporating prior history of influenza vaccination. We included specimens from 9,982 patient hospitalization episodes over four seasons, with 12.8% testing positive for influenza. We observed variation in VE by vaccination status, age group, and influenza season. For the four seasons combined, VE was 60% (95%CI, 44%-72%) for full vaccination and 39% (95%CI, 17%-56%) for partial vaccination. VE for full vaccination was 67% (95%CI, 48%-79%) for children aged 24-59 months, 48% (95%CI, 12%-69%) for children aged 6-23 months, 77% (95%CI, 47%-90%) for 2010-11, 59% (95%CI, 13%-81%) for 2011-12, 33% (95%CI, -18% to 62%) for 2012-13, and 72% (95%CI, 42%-86%) for 2013-14. VE in children aged 24-59 months appeared similar between those vaccinated in both the current and previous seasons and those vaccinated in the current season only, with the exception of 2012-13, when VE was lower for those vaccinated in the current season only. Influenza vaccination is effective in preventing pediatric laboratory-confirmed influenza hospitalizations during most seasons.

Influenza vaccines for preventing acute otitis media in infants and children

BACKGROUND

Acute otitis media (AOM) is one of the most common infectious diseases in children. It has been reported that 64% of infants have an episode of AOM by the age of six months and 86% by one year. Although most cases of AOM are due to bacterial infection, it is commonly triggered by a viral infection. In most children AOM is self limiting, but it does carry a risk of complications. Since antibiotic treatment increases the risk of antibiotic resistance, influenza vaccines might be an effective way of reducing this risk by preventing the development of AOM.

OBJECTIVES

To assess the effectiveness of influenza vaccine in reducing the occurrence of acute otitis media in infants and children.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, CINAHL, LILACS, Web of Science, the WHO International Clinical Trials Registry Platform, and ClinicalTrials.gov (15 February 2017). We also searched the reference lists of included studies to identify any additional trials.

SELECTION CRITERIA

Randomised controlled trials comparing influenza vaccine with placebo or no treatment in infants and children aged younger than six years. We included children of either sex and of any ethnicity, with or without a history of recurrent AOM.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened studies, assessed trial quality, and extracted data. We performed statistical analyses using the random-effects and fixed-effect models and expressed the results as risk ratio (RR), risk difference (RD), and number needed to treat for an additional beneficial outcome (NNTB) for dichotomous outcomes, with 95% confidence intervals (CI).

MAIN RESULTS

We included 11 trials (6 trials in high-income countries and 5 multicentre trials in high-, middle-, and low-income countries) involving 17,123 children aged 6 months to 6 years. Eight trials recruited participants from a healthcare setting. Ten trials (and all four trials that contributed to the primary outcome) declared funding from vaccine manufacturers. Four trials reported adequate allocation concealment, and 10 trials reported adequate blinding of participants and personnel. Attrition was low for eight trials included in the analysis.The primary outcome showed a small reduction in at least one episode of AOM over at least six months of follow-up (4 trials, 3134 children; RR 0.84, 95% CI 0.69 to 1.02; RD -0.04, 95% CI -0.08 to -0.00; NNTB 25, 95% CI 12.5 to 100; low-quality evidence).The subgroup analyses (i.e. number of courses and types of vaccine administered) showed no differences.There was a reduction in the use of antibiotics in vaccinated children (2 trials, 1223 children; RR 0.70, 95% CI 0.59 to 0.83; RD -0.11, 95% CI -0.16 to -0.06; moderate-quality evidence).We were unable to demonstrate whether there was any difference in the utilisation of health care. The use of influenza vaccine resulted in a significant increase in fever (7 trials, 10,615 children; RR 1.15, 95% CI 1.06 to 1.24; RD 0.02, 95% CI 0.00 to 0.04; low-quality evidence), rhinorrhoea (6 trials, 10,563 children; RR 1.17, 95% CI 1.07 to 1.29; RD 0.09, 95% CI 0.01 to 0.16; low-quality evidence), but no difference in pharyngitis. No major adverse events were reported.Differing from the protocol, the original publication of the review included a subgroup analysis of AOM episodes by season, and the secondary outcome 'types of influenza vaccine' was changed to a subgroup analysis. For this update, we removed the subgroup analyses for trial setting, season, and utilisation of health care due to the small number of trials involved. We removed Belshe 2000 from primary and secondary outcomes (courses of vaccine and types of vaccine) because it reported episodes of AOM per person. We did not perform a subgroup analysis by type of adverse event. We have reported each type of adverse event as a separate analysis.

AUTHORS' CONCLUSIONS

Influenza vaccine results in a small reduction in AOM. The observed reduction in the use of antibiotics needs to be considered in light of current recommended practices aimed at avoiding antibiotic overuse. Safety data from these trials were limited. The benefits may not justify the use of influenza vaccine without taking into account the vaccine efficacy in reducing influenza and safety data. We judged the quality of the evidence to be low to moderate. Additional research is needed.

Potential Consequences of Not Using Live Attenuated Influenza Vaccine

INTRODUCTION

Decreased live attenuated influenza vaccine (LAIV) effectiveness in the U.S. prompted the Advisory Committee on Immunization Practices in August 2016 to recommend against this vaccine's use. However, overall influenza uptake increases when LAIV is available and, unlike the U.S., LAIV has retained its effectiveness in other countries. These opposing countercurrents create a dilemma.

METHODS

To examine the potential consequences of the decision to not recommend LAIV, which may result in decreased influenza vaccination coverage in the U.S. population, a Markov decision analysis model was used to examine influenza vaccination options in U.S. children aged 2-8 years. Data were compiled and analyzed in 2016.

RESULTS

Using recently observed low LAIV effectiveness values, fewer influenza cases will occur if LAIV is not used compared with having LAIV as a vaccine option. However, having the option to use LAIV may be favored if LAIV effectiveness returns to prior levels or if the absence of vaccine choice substantially decreases overall vaccine uptake.

CONCLUSIONS

Continued surveillance of LAIV effectiveness and influenza vaccine uptake is warranted, given their importance in influenza vaccination policy decisions.

Factors associated with the uptake of seasonal influenza vaccination in older and younger adults: a large, population-based survey in Beijing, China

OBJECTIVES

The present study aimed to estimate the influenza vaccination coverage rate in Beijing, China, and identify its determinants in older and younger adults.

METHODS

A survey was conducted among Chinese adults using a self-administered, anonymous questionnaire in May-June 2015. The main outcome was seasonal influenza vaccination uptake. Multivariate logistic regression models were performed to identify factors associated with uptake.

RESULTS

A total of 7106 participants completed the questionnaire. The overall coverage rate was 20.6% (95% CI 19.7% to 21.5%) in the 2014/2015 influenza season. Lower education (older adults: OR 1.6; 95% CI 1.2 to 2.1; younger adults: OR 1.9; 95% CI 1.4 to 2.6), having a chronic illness (older adults: OR 1.9; 95% CI 1.5 to 2.4; younger adults: OR 1.4; 95% CI 1.2 to 1.7) and recommendations from healthcare workers (older adults: OR 5.4; 95% CI 3.9 to 7.4; younger adults: OR 4.5; 95% CI 3.7 to 5.4) were positively associated with uptake; perceived side effects of vaccination had a negative impact (older adults: OR 0.6; 95% CI 0.4 to 0.7; younger adults: OR 0.8; 95% CI 0.7 to 1.0). Perceived susceptibility to influenza (OR 1.5; 95% CI 1.2 to 2.0) and awareness of the free influenza vaccine policy (OR 1.9; 95% CI 1.2 to 2.9) were only associated with vaccine uptake in older adults, while perceived effectiveness of vaccination (OR 2.2; 95% CI 1.7 to 2.8) was only a predictor for younger adults. Older adults were more likely to receive recommendations from healthcare professionals and perceive the severity of seasonal influenza, and less likely to worry about side effects of vaccination.

CONCLUSION

The influenza vaccination coverage rate was relatively low in Beijing. Apart from free vaccinations for older adults, age disparity in the rate between older and younger adults (48.7% vs 16.0%) may be explained by differing professional recommendations and public perceptions. Vaccination campaigns targeting increasing professional recommendations and public perceptions should be implemented in the coming years.

Variation in loss of immunity shapes influenza epidemics and the impact of vaccination

BACKGROUND

Protective antibody immunity against the influenza A virus wanes in 2-7 years due to antigenic drift of the virus' surface proteins. The duration of immune protection is highly variable because antigenic evolution of the virus is irregular. Currently, the variable nature of the duration of immunity has had little attention in analyses of the impact of vaccination, including cost-effectiveness studies.

METHODS

We developed a range of mathematical transmission models to investigate the effect of variable duration of immunity on the size of seasonal epidemics. The models range from simple conceptual to more realistic, by distinguishing between infection- versus vaccination-induced immunity, by inclusion of primary vaccine failure, by assuming a leaky vaccine, and by the inclusion of age-dependent contact patterns.

RESULTS

We show that annual variation in the duration of immunity causes large variation in the size of epidemics, and affects the effectiveness of vaccination. Accumulation of susceptible individuals in one or more mild seasons results in a disproportionately large outbreak in a subsequent season. Importantly, variation in the duration of immunity increases the average infection attack rate when the vaccination coverage is around the outbreak threshold. Specifically, in a tailored age-stratified model with a realistic reproduction number (R ₀ = 1.4) and vaccination coverage of 25%, we find that the attack rate in unvaccinated children (<10 years old) is negligible if the duration of immunity is constant, while on average 2.8% (2.5-97.5% percentiles: 1.8-4.1%) of the children are infected if the duration of immunity is variable. These findings stem from the buildup of susceptibility over multiple seasons by waning of immunity, and the nonlinear relation between susceptibility and infection attack rates.

CONCLUSIONS

The models illustrate that variation in the duration of immunity impacts the long-term effectiveness of vaccination, and that vaccine effectiveness cannot be judged for each year in isolation. Our findings have implications for vaccination strategies that aim to maximize the vaccination coverage while extending the age range of persons eligible for vaccination.

Influenzanet: Citizens Among 10 Countries Collaborating to Monitor Influenza in Europe

Background

The wide availability of the Internet and the growth of digital communication technologies have become an important tool for epidemiological studies and health surveillance. Influenzanet is a participatory surveillance system monitoring the incidence of influenza-like illness (ILI) in Europe since 2003. It is based on data provided by volunteers who self-report their symptoms via the Internet throughout the influenza season and currently involves 10 countries.

Objective

In this paper, we describe the Influenzanet system and provide an overview of results from several analyses that have been performed with the collected data, which include participant representativeness analyses, data validation (comparing ILI incidence rates between Influenzanet and sentinel medical practice networks), identification of ILI risk factors, and influenza vaccine effectiveness (VE) studies previously published. Additionally, we present new VE analyses for the Netherlands, stratified by age and chronic illness and offer suggestions for further work and considerations on the continuity and sustainability of the participatory system.

Methods

Influenzanet comprises country-specific websites where residents can register to become volunteers to support influenza surveillance and have access to influenza-related information. Participants are recruited through different communication channels. Following registration, volunteers submit an intake questionnaire with their postal code and sociodemographic and medical characteristics, after which they are invited to report their symptoms via a weekly electronic newsletter reminder. Several thousands of participants have been engaged yearly in Influenzanet, with over 36,000 volunteers in the 2015-16 season alone.

Results

In summary, for some traits and in some countries (eg, influenza vaccination rates in the Netherlands), Influenzanet participants were representative of the general population. However, for other traits, they were not (eg, participants underrepresent the youngest and oldest age groups in 7 countries). The incidence of ILI in Influenzanet was found to be closely correlated although quantitatively higher than that obtained by the sentinel medical practice networks. Various risk factors for acquiring an ILI infection were identified. The VE studies performed with Influenzanet data suggest that this surveillance system could develop into a complementary tool to measure the effectiveness of the influenza vaccine, eventually in real time.

Conclusions

Results from these analyses illustrate that Influenzanet has developed into a fast and flexible monitoring system that can complement the traditional influenza surveillance performed by sentinel medical practices. The uniformity of Influenzanet allows for direct comparison of ILI rates between countries. It also has the important advantage of yielding individual data, which can be used to identify risk factors. The way in which the Influenzanet system is constructed allows the collection of data that could be extended beyond those of ILI cases to monitor pandemic influenza and other common or emerging diseases.

Influenza vaccine use to protect healthy children: A debated topic

At the beginning of this century, a number of studies suggested that in healthy children, particularly those <2years of age, influenza could have a serious and complicated course, as it frequently led to hospitalization and sometimes, albeit rarely, to death. Moreover, pre-schoolers and school-age children were found to be among the most important causes of influenza transmission to the community, as they shed the virus for a longer time than adults and had frequent contact with greater numbers of individuals through day-care and school. These findings led a number of health authorities to modify the official recommendations regarding the use of influenza vaccine in healthy children. Several factors seem to indicate that vaccination against influenza in healthy children of any age and in pregnant women could be effective in preventing the disease in the entire paediatric population and in providing herd immunity in adults and old people as well. The direct advantages of the vaccine seem greater in younger subjects, particularly those <2-3years of age. Vaccination of older children is considered effective by most experts, but high vaccination coverage of these subjects has been difficult to attain. Similar difficulties have been identified for the vaccination of pregnant women. These challenges can be overcome, at least in part, by appropriate information and accurate evaluations of available data. In addition, further studies specifically designed to clarify unresolved problems regarding vaccine use in paediatric and pregnant populations are needed to convince reluctant health authorities. More effective vaccines for younger children as well as improved availability of data regarding the optimal time period for vaccine administration in pregnant women appear relevant in this regard.

National assessment of Canadian pandemic preparedness: Employing InFluNet to identify high-risk areas for inter-wave vaccine distribution

BACKGROUND

Influenza pandemics emerge at irregular and unpredictable intervals to cause substantial health, economic and social burdens. Optimizing health-system response is vital to mitigating the consequences of future pandemics.

METHODS

We developed a mathematical model to assess the preparedness of Canadian health systems to accommodate pandemic-related increases in patient demand. We identify vulnerable areas, assess the potential of inter-wave vaccination to mitigate impacts and evaluate the association between demographic and health-system characteristics in order to identify predictors of pandemic consequences.

RESULTS

Modelled average attack rates were 23.7-37.2% with no intervention and 2.5-6.4% with pre-vaccination. Peak acute-care demand was 7.5-19.5% of capacity with no intervention and 0.6-2.6% with pre-vaccination. The peak ICU demand was 39.3-101.8% with no intervention and 2.9-13.3% with pre-vaccination. Total mortality was 2258-7944 with no intervention and 88-472 with pre-vaccination. Regions of Southern Ontario were identified as most vulnerable to surges in patient demand. The strongest predictors of peak acute-care demand and ICU demand were acute-care bed capacity (R = -0.8697; r2 = 0.7564) and ICU bed capacity (R = -0.8151; r2 = 0.6644), respectively. Demographic characteristics had mild associations with predicted pandemic consequences.

CONCLUSION

Inter-wave vaccination provided adequate acute-care resource protection under all scenarios; ICU resource adequacy was protected under mild disease assumptions, but moderate and severe diseases caused demand to exceed expected availability in 21% and 49% of study areas, respectively. Our study informs priority vaccine distribution strategies for pandemic planning, emphasizing the need for targeted early vaccine distribution to high-risk individuals and areas.

Influenza vaccine effectiveness among high-risk groups: A systematic literature review and meta-analysis of case-control and cohort studies

Vaccination represents the most effective intervention to prevent infection, hospitalization and mortality due to influenza. This meta-analysis quantifies data reporting influenza vaccine effectiveness (VE) on influenza visits and hospitalizations of case-control and cohort studies among high-risk groups.

A systematic literature review including original articles published between 2007 and 2016, using a protocol registered on Prospero with No. 42017054854, and a meta-analysis were conducted.

For 3 high-risk groups (subjects with underlying health conditions, pregnant women and health care workers) only a qualitative evaluation was performed. The VE quantitative analysis demonstrated a clear significant overall effect of 39% (95%CI: 32–46%) for visits and 57% (95%CI: 30–74%) for hospitalization among children. Considering the elderly influenza VE had a clear effect of 25% (95%CI: 6–40%) for visits and 14% (95%CI: 7–21%; p<0.001) for hospitalization.

This study showed the high VE of influenza vaccination among high-risk groups, representing a tool for public health decision-makers to develop evidence-based preventive interventions to avoid influenza outcomes.

Vaccines for the common cold

BACKGROUND

The common cold is a spontaneously remitting infection of the upper respiratory tract, characterised by a runny nose, nasal congestion, sneezing, cough, malaise, sore throat, and fever (usually < 37.8º C). The widespread morbidity caused by the common cold worldwide is related to its ubiquitousness rather than its severity. The development of vaccines for the common cold has been difficult because of antigenic variability of the common cold virus and the indistinguishable multiple other viruses and even bacteria acting as infective agents. There is uncertainty regarding the efficacy and safety of interventions for preventing the common cold in healthy people. This is an update of a Cochrane review first published in 2011 and previously updated in 2013.

OBJECTIVES

To assess the clinical effectiveness and safety of vaccines for preventing the common cold in healthy people.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (September 2016), MEDLINE (1948 to September 2016), Embase (1974 to September 2016), CINAHL (1981 to September 2016), and LILACS (1982 to September 2016). We also searched three trials registers for ongoing studies and four websites for additional trials (February 2017). We included no language or date restrictions.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of any virus vaccines compared with placebo to prevent the common cold in healthy people.

DATA COLLECTION AND ANALYSIS

Two review authors independently evaluated methodological quality and extracted trial data. We resolved disagreements by discussion or by consulting a third review author.

MAIN RESULTS

We found no additional RCTs for inclusion in this update. This review includes one RCT dating from the 1960s with an overall high risk of bias. The RCT included 2307 healthy participants, all of whom were included in analyses. This trial compared the effect of an adenovirus vaccine against placebo. No statistically significant difference in common cold incidence was found: there were 13 (1.14%) events in 1139 participants in the vaccines group and 14 (1.19%) events in 1168 participants in the placebo group (risk ratio 0.95, 95% confidence interval 0.45 to 2.02; P = 0.90). No adverse events related to the live vaccine were reported. The quality of the evidence was low due to limitations in methodological quality and a wide 95% confidence interval.

AUTHORS' CONCLUSIONS

This Cochrane Review was based on one study with low-quality evidence. We found no conclusive results to support the use of vaccines for preventing the common cold in healthy people compared with placebo. We identified a need for well-designed, adequately powered RCTs to investigate vaccines for the common cold in healthy people. Any future trials on medical treatments for preventing the common cold should assess a variety of virus vaccines for this condition. Outcome measures should include common cold incidence, vaccine safety, and mortality related to the vaccine.

Direct and indirect effects of influenza vaccination

BACKGROUND

After vaccination, vaccinees acquire some protection against infection and/or disease. Vaccination, therefore, reduces the number of infections in the population. Due to this herd protection, not everybody needs to be vaccinated to prevent infections from spreading.

METHODS

We quantify direct and indirect effects of influenza vaccination examining the standard Susceptible-Infected-Recovered (SIR) and Susceptible-Infected-Recovered-Susceptible (SIRS) model as well as simulation results of a sophisticated simulation tool which allows for seasonal transmission of four influenza strains in a population with realistic demography and age-dependent contact patterns.

RESULTS

As shown analytically for the simple SIR and SIRS transmission models, indirect vaccination effects are bigger than direct ones if the effective reproduction number of disease transmission is close to the critical value of 1. Simulation results for 20-60% vaccination with live influenza vaccine of 2-17 year old children in Germany, averaged over 10 years (2017-26), confirm this result: four to seven times as many influenza cases are prevented among non-vaccinated individuals as among vaccinees. For complications like death due to influenza which occur much more frequently in the unvaccinated elderly than in the vaccination target group of children, indirect benefits can surpass direct ones by a factor of 20 or even more than 30.

CONCLUSIONS

The true effect of vaccination can be much bigger than what would be expected by only looking at vaccination coverage and vaccine efficacy.

Case-control vaccine effectiveness studies: Data collection, analysis and reporting results

The case-control methodology is frequently used to evaluate vaccine effectiveness post-licensure. The results of such studies provide important insight into the level of protection afforded by vaccines in a 'real world' context, and are commonly used to guide vaccine policy decisions. However, the potential for bias and confounding are important limitations to this method, and the results of a poorly conducted or incorrectly interpreted case-control study can mislead policies. In 2012, a group of experts met to review recent experience with case-control studies evaluating vaccine effectiveness; we summarize the recommendations of that group regarding best practices for data collection, analysis, and presentation of the results of case-control vaccine effectiveness studies. Vaccination status is the primary exposure of interest, but can be challenging to assess accurately and with minimal bias. Investigators should understand factors associated with vaccination as well as the availability of documented vaccination status in the study context; case-control studies may not be a valid method for evaluating vaccine effectiveness in settings where many children lack a documented immunization history. To avoid bias, it is essential to use the same methods and effort gathering vaccination data from cases and controls. Variables that may confound the association between illness and vaccination are also important to capture as completely as possible, and where relevant, adjust for in the analysis according to the analytic plan. In presenting results from case-control vaccine effectiveness studies, investigators should describe enrollment among eligible cases and controls as well as the proportion with no documented vaccine history. Emphasis should be placed on confidence intervals, rather than point estimates, of vaccine effectiveness. Case-control studies are a useful approach for evaluating vaccine effectiveness; however careful attention must be paid to the collection, analysis and presentation of the data in order to best inform evidence-based vaccine policies.

Case-control vaccine effectiveness studies: Preparation, design, and enrollment of cases and controls

Case-control studies are commonly used to evaluate effectiveness of licensed vaccines after deployment in public health programs. Such studies can provide policy-relevant data on vaccine performance under ‘real world’ conditions, contributing to the evidence base to support and sustain introduction of new vaccines. However, case-control studies do not measure the impact of vaccine introduction on disease at a population level, and are subject to bias and confounding, which may lead to inaccurate results that can misinform policy decisions. In 2012, a group of experts met to review recent experience with case-control studies evaluating the effectiveness of several vaccines; here we summarize the recommendations of that group regarding best practices for planning, design and enrollment of cases and controls. Rigorous planning and preparation should focus on understanding the study context including healthcare-seeking and vaccination practices. Case-control vaccine effectiveness studies are best carried out soon after vaccine introduction because high coverage creates strong potential for confounding. Endpoints specific to the vaccine target are preferable to non-specific clinical syndromes since the proportion of non-specific outcomes preventable through vaccination may vary over time and place, leading to potentially confusing results. Controls should be representative of the source population from which cases arise, and are generally recruited from the community or health facilities where cases are enrolled. Matching of controls to cases for potential confounding factors is commonly used, although should be reserved for a limited number of key variables believed to be linked to both vaccination and disease. Case-control vaccine effectiveness studies can provide information useful to guide policy decisions and vaccine development, however rigorous preparation and design is essential.

Evaluating the effectiveness, impact and safety of live attenuated and seasonal inactivated influenza vaccination: protocol for the Seasonal Influenza Vaccination Effectiveness II (SIVE II) study

INTRODUCTION

Seasonal (inactivated) influenza vaccination is recommended for all individuals aged 65+ and in individuals under 65 who are at an increased risk of complications of influenza infection, for example, people with asthma. Live attenuated influenza vaccine (LAIV) was recommended for children as they are thought to be responsible for much of the transmission of influenza to the populations at risk of serious complications from influenza. A phased roll-out of the LAIV pilot programme began in 2013/2014. There is limited evidence for vaccine effectiveness (VE) in the populations targeted for influenza vaccination. The aim of this study is to examine the safety and effectiveness of the live attenuated seasonal influenza vaccine programme in children and the inactivated seasonal influenza vaccination programme among different age and at-risk groups of people.

METHODS AND ANALYSIS

Test negative and cohort study designs will be used to estimate VE. A primary care database covering 1.25 million people in Scotland for the period 2000/2001 to 2015/2016 will be linked to the Scottish Immunisation Recall Service (SIRS), Health Protection Scotland virology database, admissions to Scottish hospitals and the Scottish death register. Vaccination status (including LAIV uptake) will be determined from the primary care and SIRS database. The primary outcome will be influenza-positive real-time PCR tests carried out in sentinel general practices and other healthcare settings. Secondary outcomes include influenza-like illness and asthma-related general practice consultations, hospitalisations and death. An instrumental variable analysis will be carried out to account for confounding. Self-controlled study designs will be used to estimate the risk of adverse events associated with influenza vaccination.

ETHICS AND DISSEMINATION

We obtained approval from the National Research Ethics Service Committee, West Midlands-Edgbaston. The study findings will be presented at international conferences and published in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

ISRCTN88072400; Pre-results.

Industry sponsorship and research outcome

BACKGROUND

Clinical research affecting how doctors practice medicine is increasingly sponsored by companies that make drugs and medical devices. Previous systematic reviews have found that pharmaceutical-industry sponsored studies are more often favorable to the sponsor's product compared with studies with other sources of sponsorship. A similar association between sponsorship and outcomes have been found for device studies, but the body of evidence is not as strong as for sponsorship of drug studies. This review is an update of a previous Cochrane review and includes empirical studies on the association between sponsorship and research outcome.

OBJECTIVES

To investigate whether industry sponsored drug and device studies have more favorable outcomes and differ in risk of bias, compared with studies having other sources of sponsorship.

SEARCH METHODS

In this update we searched MEDLINE (2010 to February 2015), Embase (2010 to February 2015), the Cochrane Methodology Register (2015, Issue 2) and Web of Science (June 2015). In addition, we searched reference lists of included papers, previous systematic reviews and author files.

SELECTION CRITERIA

Cross-sectional studies, cohort studies, systematic reviews and meta-analyses that quantitatively compared primary research studies of drugs or medical devices sponsored by industry with studies with other sources of sponsorship. We had no language restrictions.

DATA COLLECTION AND ANALYSIS

Two assessors screened abstracts and identified and included relevant papers. Two assessors extracted data, and we contacted authors of included papers for additional unpublished data. Outcomes included favorable results, favorable conclusions, effect size, risk of bias and whether the conclusions agreed with the study results. Two assessors assessed risk of bias of included papers. We calculated pooled risk ratios (RR) for dichotomous data (with 95% confidence intervals (CIs)).

MAIN RESULTS

Twenty-seven new papers were included in this update and in total the review contains 75 included papers. Industry sponsored studies more often had favorable efficacy results, RR: 1.27 (95% CI: 1.17 to 1.37) (25 papers) (moderate quality evidence), similar harms results RR: 1.37 (95% CI: 0.64 to 2.93) (four papers) (very low quality evidence) and more often favorable conclusions RR: 1.34 (95% CI: 1.19 to 1.51) (29 papers) (low quality evidence) compared with non-industry sponsored studies. Nineteen papers reported on sponsorship and efficacy effect size, but could not be pooled due to differences in their reporting of data and the results were heterogeneous. We did not find a difference between drug and device studies in the association between sponsorship and conclusions (test for interaction, P = 0.98) (four papers). Comparing industry and non-industry sponsored studies, we did not find a difference in risk of bias from sequence generation, allocation concealment, follow-up and selective outcome reporting. However, industry sponsored studies more often had low risk of bias from blinding, RR: 1.25 (95% CI: 1.05 to 1.50) (13 papers), compared with non-industry sponsored studies. In industry sponsored studies, there was less agreement between the results and the conclusions than in non-industry sponsored studies, RR: 0.83 (95% CI: 0.70 to 0.98) (six papers).

AUTHORS' CONCLUSIONS

Sponsorship of drug and device studies by the manufacturing company leads to more favorable efficacy results and conclusions than sponsorship by other sources. Our analyses suggest the existence of an industry bias that cannot be explained by standard 'Risk of bias' assessments.

Public health impact and economic benefits of quadrivalent influenza vaccine in Latin America

Annual trivalent influenza vaccines (TIV) containing 2 A strains and one B lineage have been recommended for the prevention of influenza in most of Latin American countries. However, the circulation of 2 B lineages (Victoria and Yamagata) and difficulties in predicting the predominating lineage have led to the development of quadrivalent influenza vaccines (QIV), including both B lineages. Thus, the objective was to estimate the public health impact and influenza-related costs if QIV would have been used instead of TIV in 3 Latin American countries. We used a static model over the seasons 2010–2014 in Brazil, 2007–2014 in Colombia and 2006–2014 in Panama, focusing on population groups targeted by local vaccination recommendations: young children, adults with risk factors and the elderly. In Brazil, between 2010 and 2014, using QIV instead of TIV would have avoided US$ 6,200 per 100,000 person-years in societal costs, based on 168 influenza cases, 89 consultations, 3.2 hospitalizations and 0.38 deaths per 100,000 person-years. In Colombia and Panama, these would have ranged from US$ 1,000 to 12,700 (based on 34 cases, 13–25 consultations, 0.6–8.9 hospitalizations and 0.04–1.74 deaths) and from US$ 3,000 to 33,700 (based on 113 cases, 55–82 consultations, 0.5–27.8 hospitalizations and 0.08–6.87 deaths) per 100,000 person-years, respectively. Overall, the broader protection offered by QIV would have reduced the influenza humanistic and economic burden in the 3 countries. Despite the lack of local data leading to several extrapolations, this study is the first to give quantitative estimates of the potential benefits of QIV in Latin America.

Trivalent inactivated influenza vaccine effective against influenza A(H3N2) variant viruses in children during the 2014/15 season, Japan

The 2014/15 influenza season in Japan was characterised by predominant influenza A(H3N2) activity; 99% of influenza A viruses detected were A(H3N2). Subclade 3C.2a viruses were the major epidemic A(H3N2) viruses, and were genetically distinct from A/New York/39/2012(H3N2) of 2014/15 vaccine strain in Japan, which was classified as clade 3C.1. We assessed vaccine effectiveness (VE) of inactivated influenza vaccine (IIV) in children aged 6 months to 15 years by test-negative case–control design based on influenza rapid diagnostic test. Between November 2014 and March 2015, a total of 3,752 children were enrolled: 1,633 tested positive for influenza A and 42 for influenza B, and 2,077 tested negative. Adjusted VE was 38% (95% confidence intervals (CI): 28 to 46) against influenza virus infection overall, 37% (95% CI: 27 to 45) against influenza A, and 47% (95% CI: -2 to 73) against influenza B. However, IIV was not statistically significantly effective against influenza A in infants aged 6 to 11 months or adolescents aged 13 to 15 years. VE in preventing hospitalisation for influenza A infection was 55% (95% CI: 42 to 64). Trivalent IIV that included A/New York/39/2012(H3N2) was effective against drifted influenza A(H3N2) virus, although vaccine mismatch resulted in low VE.

The Clinical and Economic Impact of Probiotics Consumption on Respiratory Tract Infections: Projections for Canada

INTRODUCTION

There is accumulating evidence supporting the use of probiotics, which are defined as "live micro-organisms which, when administered in adequate amounts, confer a health benefit on the host", as a preventive measure against respiratory tract infections (RTI). Two recent meta-analyses showed probiotic consumption (daily intake of 107 to 1010 CFU in any form for up to 3 months) significantly reduced RTI duration, frequency, antibiotic use and work absenteeism.

OBJECTIVES

The aim of this study was to assess the impact of probiotic use in terms of number of RTI episodes and days averted, and the number of antibiotic prescriptions and missed workdays averted, in the general population of Canada. In addition, the corresponding economic impact from both a healthcare payer and a productivity perspective was estimated.

METHODS

A microsimulation model was developed to reproduce the Canadian population (sample rate of 1/1000 = 35 540 individuals) employing age and gender. RTI incidence was taken from FluWatch consultation rates for influenza-like illness (2013-14) and StatCan all-cause consultations statistics. The model was calibrated on a 2.1% RTI annual incidence in the general population (5.2 million RTI days) and included known risk factors (smoking status, shared living conditions and vaccination status). RTI-related antibiotic prescriptions and work absenteeism were obtained from the literature.

RESULTS

The results indicate that probiotic use saved 573 000-2.3 million RTI-days, according to the YHEC-Cochrane scenarios respectively. These reductions were associated with an avoidance of 52 000-84 000 antibiotic courses and 330 000-500 000 sick-leave days. A projection of corresponding costs reductions amounted to Can$1.3-8.9 million from the healthcare payer perspective and Can$61.2-99.7 million when adding productivity losses.

CONCLUSION

The analysis shows that the potential of probiotics to reduce RTI-related events may have a substantial clinical and economic impact in Canada.