Vaccines for preventing influenza in healthy children

Acceptability, cost-effectiveness, and capacity of a facility-based seasonal influenza vaccination among high-risk groups: a study protocol in selected tertiary care hospitals of Bangladesh

BACKGROUND

In Bangladesh, seasonal influenza imposes considerable disease and economic burden, especially for those at high-risk of severe disease. The most successful approach for influenza prevention is the administration of a vaccine. Many poor and middle-income nations, including Bangladesh, do not have a national strategy or program in place for seasonal influenza vaccines, despite the World Health Organization's (WHO) advice to prioritize high-risk populations. Additionally, there is a scarcity of substantial data on the cost-effectiveness of seasonal influenza vaccination in these countries. The aim of our study is to determine acceptability, health beliefs, barriers, and intention of receiving influenza vaccine among high-risk populations, assess the cost-effectiveness of implementing a facility-based seasonal influenza vaccination programme, and investigate the required capacity for a potential seasonal influenza vaccination programme.

METHODS

We will undertake this study following STROBE guidelines. We will conduct the study in inpatient and outpatient departments of three selected tertiary-level hospitals leveraging the ongoing hospital-based influenza surveillance (HBIS) platform. The study population will include the WHO-defined four high-risk groups excluding healthcare workers: children six months to eight years, pregnant women, elderly ≥ 60 years, and adults with chronic diseases. We will collect quantitative data on participants' acceptability, health beliefs, barriers, and vaccination intentions using the health belief model (HBM) from patients meeting the criteria for high-risk populations attending two public tertiary-level hospitals. In one of the two public tertiary-level hospitals, we will arrange an influenza vaccination campaign before the influenza season, where the vaccine will be offered free of cost to high-risk patients, and in the second hospital, vaccination will not be offered. Both the vaccinated and unvaccinated participants will then be followed-up once a month for one year to record any influenza-like illness, hospitalization, and death. Additional data for objective two will be collected from patients with symptoms of influenza-like illness (ILI) and severe acute respiratory infection (SARI) at one public and one private hospital to determine both direct and indirect costs associated with influenza illness. We will estimate the required number of influenza vaccines, safe injections, and total storage volume utilizing secondary data. We will use a deterministic Markov decision-analytic model to estimate the cost-effectiveness of facility-based influenza vaccination in Bangladesh.

DISCUSSION

The results of this study will enable the National Immunization Technical Advisory Group and the Ministry of Health & Family Welfare of Bangladesh to decide what steps to take to develop and implement an influenza vaccination strategy targeting high-risk populations.

TRIAL REGISTRATION

The Clinicaltrials.gov registration number is NCT05996549. The registration for the protocol version 2.0 took place in August 2023, with the initial participant being enrolled in March 2022.

Trivalent inactivated influenza vaccine response and immunogenicity assessment after one week and three months in repeatedly vaccinated adults

BACKGROUND

The influenza vaccine administrated every year is a recommended infection control procedure for individuals above the age of six months. However, the effectiveness of repeated annual vaccination is still an active research topic. Therefore, we investigated the vaccine immunogenicity in two independent groups: previously vaccinated versus non-vaccinated individuals at three time points; prior vaccination, one week and three months post vaccination. The assessment enabled us to evaluate the elicited immune responses and the durability of the induced protection in both groups.

RESEARCH DESIGN AND METHODS

A research study was conducted to assess the immunogenicity of a single dose of Trivalent Inactivated Influenza Vaccine (A/H1N1, A/H3N2, and B) in 278 healthy adults aged between 32 and 66 years. Almost half of the participants, 140 (50·36%), received influenza vaccination at least once precursor to past influenza seasons. One blood sample was taken prior to vaccination for complete blood analysis and baseline immunogenicity assessment. The selected study participants received a single vaccine dose on the first day, and then followed up for three months. Two blood samples were taken after one week and three months post vaccination, respectively, for vaccine immunogenicity assessment.

RESULTS

Before vaccination, the seroprotection, defined as a hemagglutination-inhibiting titer of =>1:40, was detected for the three vaccine virus strains in 20 previously vaccinated participants (14·29%) [8·95%, 21·2%]. We compared the overall vaccine response for the three virus strains using a normalized response score calculated from linearly transformed titer measurements; the score before vaccination was 84% higher in the previously vaccinated group and the mean difference between the two groups was statistically significant. Three months post-vaccination, we didn't find a significant difference in vaccine responses; the number of fully seroprotected individuals became 48 (34·29%) [26·48%, 42·77%] in the previously vaccinated group and 59 (42·75%) [34·37%, 51·45%] in the non-vaccinated group. The calculated response score was almost equal in both groups and the mean difference was no longer statistically significant.

CONCLUSION

Our findings suggest that a single dose of influenza vaccine is equally protective after three months for annually vaccinated adults and first-time vaccine receivers.

COVID-19 Vaccines in Clinical Trials and their Mode of Action for Immunity against the Virus

For nearly two decades, coronaviruses have caused many health and economic problems, while no effective commercial vaccine has yet been developed. It is worth mentioning that despite some mutations and recombination in SARS-CoV-2, its genotype is very close to the original strain from Wuhan, China. Therefore, the development of an effective vaccine would be promising. It might be hypothesized that BCG vaccination is performed in high-risk populations before the commercialization of an effective SARS-CoV-2 vaccine. However, the development of an effective vaccine without considering the adverse immune reactions derived from antibody-dependent or cell-based immune enhancement may threaten vaccinated people's lives and long-term side effects must be considered. To this end, targeting of the receptor-binding domain (RBD) in spike and not whole spike, glycolization of FC receptors, PD-1 blockers, CPPs, etc., are promising. Therefore, the subunit vaccines or RNA vaccines that encode the RBP segment of the spike are of interest. To enhance the vaccine efficacy, its co-delivery with an adjuvant has been recommended. Nanoparticles modulate immune response with higher efficiency than the soluble form of antigens and can be functionalized with the positively charged moieties and ligands of targeted cells, such as dendritic cells, to increase cellular uptake of the antigens and their presentation on the surface of immune cells. This research aimed to discuss the COVID-19 vaccines entering the clinical trial and their mode of action effective immunity against the virus and discusses their advantages compared to each other.

Workplace influenza vaccination to reduce employee absenteeism: An economic analysis from the employers' perspective

BACKGROUND

Each year, up to 10% of unvaccinated adults contracts seasonal influenza, with half of this proportion developing symptoms. As a result, employers experience significant economic losses in terms of employee absenteeism. Influenza vaccines can be instrumental in reducing this burden. Workplace vaccination is expected to reduce employee absenteeism more than linearly as a result of positive externalities. It remains unclear whether workplace influenza vaccination yields a positive return on investment.

METHODS

We simulated the spread of influenza in the seasons 2011-12 up to 2017-18 in Belgium by means of a compartmental transmission model. We accounted for age-specific social contact patterns and included reduced contact behavior when symptomatically infected. We simulated the impact of employer-funded influenza vaccination at the workplace and performed a cost-benefit analysis to assess the employers' return on workplace vaccination. Furthermore, we look into the cost-benefit of rewarding vaccinated employees by offering an additional day off.

RESULTS

Workplace vaccination reduced the burden of influenza both on the workplace and in the population at large. Compared to the current vaccine coverage - 21% in the population at large - an employee vaccine coverage of 90% could avert an additional 355 000 cases, of which about 150 000 in the employed population and 205 000 in the unemployed population. While seasonal influenza vaccination has been cost-saving on average at about €10 per vaccinated employee, the cost-benefit analysis was prone to between-season variability.

CONCLUSIONS

Vaccinated employees can serve as a barrier to limit the spread of influenza in the population, reducing the attack rate by 78% at an employee coverage of 90%. While workplace vaccination is relatively inexpensive (due to economies of scale) and convenient, the return on investment is volatile. Government subsidies can be pivotal to encourage employers to provide vaccination at the workplace with positive externalities to society as a whole.

Cost-Effectiveness of Routine Childhood Vaccination Against Seasonal Influenza in Germany

OBJECTIVES

In Germany, routine influenza vaccination with quadrivalent influenza vaccines (QIV) is recommended and reimbursed for individuals ≥60 years of age and individuals with underlying chronic conditions. The present study examines the cost-effectiveness of a possible extension of the recommendation to include strategies of childhood vaccination against seasonal influenza using QIV.

METHODS

A dynamic transmission model was used to examine the epidemiological impact of different childhood vaccination strategies. The outputs were used in a health economic decision tree to calculate the costs per quality-adjusted life year (QALY) gained from a societal and a third-party payer (TPP) perspective. Strain-specific epidemiology, vaccine uptake, and vaccine efficacy data from the 10 non-pandemic seasons from 2003/2004 to 2013/2014 were used, and cost data were drawn mainly from a health insurance claims data analysis and supplemented by estimates from literature. Uncertainty is explored via scenario, deterministic, and probabilistic sensitivity analyses.

RESULTS

Vaccinating 2- to 9-year-olds with QIV assuming a vaccine uptake of 40% is cost-saving with a benefit-cost ratio of 1.66 from a societal perspective and an incremental cost-effectiveness ratio of €998/QALY from a TPP perspective. Lower and higher vaccine uptakes show marginal effects, while extending the target group to 2- to 17-year-olds further increases the health benefits while still being below the willingness-to-pay (WTP) threshold. Assuming no vaccine-induced herd protection has a negative effect on the cost-effectiveness ratio, but childhood vaccination remains cost-effective.

CONCLUSION

Routine childhood vaccination against seasonal influenza in Germany is most likely to be cost-saving from a societal perspective and highly cost-effective from a TPP perspective.

The Quest for a Truly Universal Influenza Vaccine

There is an unmet public health need for a universal influenza vaccine (UIV) to provide broad and durable protection from influenza virus infections. The identification of broadly protective antibodies and cross-reactive T cells directed to influenza viral targets present a promising prospect for the development of a UIV. Multiple targets for cross-protection have been identified in the stalk and head of hemagglutinin (HA) to develop a UIV. Recently, neuraminidase (NA) has received significant attention as a critical component for increasing the breadth of protection. The HA stalk-based approaches have shown promising results of broader protection in animal studies, and their feasibility in humans are being evaluated in clinical trials. Mucosal immune responses and cross-reactive T cell immunity across influenza A and B viruses intrinsic to live attenuated influenza vaccine (LAIV) have emerged as essential features to be incorporated into a UIV. Complementing the weakness of the stand-alone approaches, prime-boost vaccination combining HA stalk, and LAIV is under clinical evaluation, with the aim to increase the efficacy and broaden the spectrum of protection. Preexisting immunity in humans established by prior exposure to influenza viruses may affect the hierarchy and magnitude of immune responses elicited by an influenza vaccine, limiting the interpretation of preclinical data based on naive animals, necessitating human challenge studies. A consensus is yet to be achieved on the spectrum of protection, efficacy, target population, and duration of protection to define a “universal” vaccine. This review discusses the recent advancements in the development of UIVs, rationales behind cross-protection and vaccine designs, and challenges faced in obtaining balanced protection potency, a wide spectrum of protection, and safety relevant to UIVs.

Probiotics Reduce Health Care Cost and Societal Impact of Flu-Like Respiratory Tract Infections in the USA: An Economic Modeling Study

Acute respiratory tract infections (RTIs) of viral origin place a substantial burden on health care resources and society. Randomized controlled trials have shown positive effects of probiotics on clinical outcomes in these commonly occurring RTIs. Two meta-analyses published by the York Health Economics Consortium (YHEC) and Cochrane reported the efficacy of probiotics in reducing incidence and duration of RTIs, number of antibiotic courses, and days absent from work. The aim of this study was to assess the potential health-economic impact of probiotics on RTI-associated events and expenses in the US primary care setting. A state-transition microsimulation model reproduced a study population representative of the US national demographics for age and gender (1/1,000 sample). RTI incidence was based on the influenza-like illness outpatient consultation rate reported by the Centers for Disease Control and Prevention (CDC) FluView. Data on vaccination, on factors that negatively impact RTI outcomes, on resource utilization, and on productivity loss were obtained from US national databases. Analyses were performed for both meta-analyses independently. Outcomes included cost savings for the health care payer, related to a reduced number of RTI episodes, less outpatient consultations, and decreased medical prescriptions as well as cost savings from a broader societal perspective related to productivity loss. The analysis showed that generalized probiotic intake in the US population for 2017–2018 would have allowed cost savings for the health care payer of 4.6 million USD based on the YHEC scenario and 373 million USD for the Cochrane scenario, by averting 19 million and 54.5 million RTI sick days, respectively, compared to no probiotics. Antibiotic prescriptions decreased with 1.39–2.16 million courses, whereas absence from work decreased by 3.58–4.2 million days when applying the YHEC and Cochrane data, respectively. When productivity loss is included, total savings for society represented 784 million or 1.4 billion USD for the YHEC and Cochrane scenarios, respectively. Subgroup analyses demonstrated an incremental benefit of probiotics in at-risk groups, which might be of relevance for targeted interventions. Sensitivity analyses confirmed the robustness of the model outcomes. Our analysis demonstrated a positive impact of probiotics on the health care and economic burden of flu-like RTIs. Improved disease outcomes translated into considerable cost savings for both the payer and society.

Indirect protection from vaccinating children against influenza in households

Vaccination is an important intervention to prevent influenza virus infection, but indirect protection of household members of vaccinees is not fully known. Here, we analyze a cluster household randomized controlled trial, with one child in each household randomized to receive influenza vaccine or placebo, for an influenza B epidemic in Hong Kong. We apply statistical models to estimate household transmission dynamics and quantify the direct and indirect protection of vaccination. Direct vaccine efficacy was 71%. The infection probability of unvaccinated household members in vaccinated households was only 5% lower than in control households, because only 10% of infections are attributed to household transmission. Even when that proportion rises to 30% and all children are vaccinated, we predict that the infection probability for unvaccinated household members would only be reduced by 20%. This suggests that benefits of individual vaccination remain important even when other household members are vaccinated.

Relevance of indirect protection of household members of vaccinees is unclear. Here, Tsang et al. quantify the direct and indirect protection of vaccination in a randomized controlled trial and show that benefits of individual vaccination remain important even when other household members are vaccinated.

Safety of Russian-Backbone Trivalent, Live Attenuated Seasonal Influenza Vaccine in Healthy Subjects: Open-Label, Non-randomized Phase 4 Study

INTRODUCTION AND AIM

A trivalent live attenuated influenza vaccine (Nasovac-S^®) was developed and licensed in India. A phase 4 study was conducted to assess safety.

METHODOLOGY

This non-randomized, open-label, single-arm study among individuals ≥ 2 years of age involved administration of 0.5 mL of Nasovac-S intranasally, with a 1-month follow-up after vaccination. Adverse events (AEs) were collected via structured diaries.

RESULTS

Among 500 vaccinated subjects, 160 were between 2 and 17 years of age, 240 were 18-49 years old and 100 were 50 years and older. A total of 533 solicited reactions were reported. The majority of these reactions were mild, and almost all of them resolved without any sequelae. A total of 20% of subjects reported at least one local solicited reaction, and 23% reported at least one systemic solicited reaction. None of the 45 unsolicited AEs reported by 37 subjects (7.4%) were causally related to the study vaccine.

CONCLUSIONS

The data from the study adds to the existing safety database of Nasovac-S.

REGISTRY

Clinical Trials Registry of India (CTRI/2015/08/006074).

Clinical Expectations for Better Influenza Virus Vaccines-Perspectives from the Young Investigators' Point of View

The influenza virus is one of a few viruses that is capable of rendering an otherwise healthy person acutly bedridden for several days. This impressive knock-out effect, without prodromal symptoms, challenges our immune system. The influenza virus undergoes continuous mutations, escaping our pre-existing immunity and causing epidemics, and its segmented genome is subject to reassortment, resulting in novel viruses with pandemic potential. The personal and socieoeconomic burden from influenza is high. Vaccination is the most cost-effective countermeasure, with several vaccines that are available. The current limitations in vaccine effectivness, combined with the need for yearly updating of vaccine strains, is a driving force for research into developing new and improved influenza vaccines. The lack of public concern about influenza severity, and misleading information concerning vaccine safety contribute to low vaccination coverage even in high-risk groups. The success of future influeza vaccines will depend on an increased public awarness of the disease, and hence, the need for vaccination-aided through improved rapid diagnositics. The vaccines must be safe and broadly acting, with new, measurable correlates of protection and robust post-marketing safety studies, to improve the confidence in influenza vaccines.

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.

WHO guide on the economic evaluation of influenza vaccination

Influenza is responsible for substantial morbidity and mortality across the globe, with a large share of the total disease burden occurring in low- and middle-income countries (LMICs). There have been relatively few economic evaluations assessing the value of seasonal influenza vaccination in LMICs. The purpose of this guide is to outline the key theoretical concepts and best practice in methodologies and to provide guidance on the economic evaluation of influenza vaccination in LMICs. It outlines many of the influenza vaccine-specific challenges and should help to provide a framework for future evaluations in the area to build upon.

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.

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.

Translation of the UK Pediatric Influenza Vaccination Programme in Primary Schools to 13 European Countries Using a Dynamic Transmission Model

Objectives: To simulate the impact of a pediatric influenza vaccination programme using quadrivalent live attenuated influenza vaccine (QLAIV) in Europe by applying coverage rates achieved in the United Kingdom during the 2014-2015 season and to compare the model outcomes to the UK results. Methods: We used a deterministic, age-structured, dynamic transmission model adapted to the demography, contact patterns and influenza incidence of 13 European countries, with a 10-year horizon. The reference strategy was the unchanged country-specific coverage rate, using quadrivalent inactivated vaccine (assumed efficacy against infection from 45% in 1-year-old children to 60% in healthy adults). In the evaluated strategy, 56.8% of 5-10-year-old children were additionally vaccinated with QLAIV (assumed efficacy 80%), as was the case in 2014-2015 in the United Kingdom's primary school pilot areas. Symptomatic influenza cases and associated medical resources (primary care consultations [PCC], hospitalization, intensive care unit [ICU] admissions) were calculated. The evaluated versus reference strategies were compared using odds ratios (ORs) for PCC in the target (aged 5-10-years) and non-target adult (aged >17 years) populations as well as number needed to vaccinate (NNV) with QLAIV to avert one PCC, hospitalization or ICU admission. Model outcomes, averaged over 10 seasons, were compared with published real-life data from the United Kingdom for the 2014-2015 season. Results: Over 13 countries and 10 years, the evaluated strategy prevented 32.8 million of symptomatic influenza cases (172.3 vs 205.2 million). The resulting range of ORs for PCC was 0.18-0.48 among children aged 5-10-years, and the published OR in the United Kingdom was 0.06 (95% confidence interval [0.01; 0.62]). In adults, the range of ORs for PCC was 0.60-0.91 (UK OR=0.41 [0.19; 0.86]). NNV ranges were 6-19 per averted PCC (UK NNV=16), 530-1524 per averted hospitalization (UK NNV=317) and 5298-15 241 per averted ICU admission (UK NNV=2205). Conclusions: Across a range of European countries, our model shows the beneficial direct and indirect impact of a paediatric vaccination programme using QLAIV in primary school-aged children, consistent with what was observed during a single season in the United Kingdom. Recommendations for the implementation of pediatric vaccination programmes are, therefore, supported in Europe.

Direct and Indirect Protection with Pediatric Quadrivalent Live-Attenuated Influenza Vaccination in Europe Estimated by a Dynamic Transmission Model

Objectives: To estimate the public health impact of annual vaccination of children with a quadrivalent live-attenuated influenza vaccine (QLAIV) across Europe. Methods: A deterministic, age-structured, dynamic model was used to simulate influenza transmission across 14 European countries, comparing current vaccination coverage using a quadrivalent inactivated vaccine (QIV) to a scenario whereby vaccination coverage was extended to 50% of 2-17 year-old children, using QLAIV. Differential equations described demographic changes, exposure to infectious individuals, recovery and immunity dynamics. For each country, the basic reproduction number (R0) was calibrated to published influenza incidence statistics. Assumed vaccine efficacy for children was 80% (QLAIV) and 59% (QIV). Symptomatic cases cumulated over 10 years were calculated per 100 000 person-years. One-way sensitivity analyses were conducted on QLAIV efficacy in 7-17 year-olds (59% instead of 80%), durations of natural (±3 years; base case: 6, 12 years for influenza A, B respectively) and QLAIV vaccine-induced immunity (100% immunity loss after 1 season; base case: 30%), and R0 (+/-10% around all-year average value). Results: Across countries, annual QLAIV vaccination additionally prevents 1366-3604 symptomatic cases per 100 000 population (average 2495 /100 000, ie, a reduction of 47.6% of the cases which occur in the reference scenario with QIV vaccination only). Among children (2-17 years), QLAIV prevents 551-1555 cases per 100 000 population (average 990 /100 000, ie, 67.2% of current cases). Among adults, QLAIV indirectly prevents 726-2047 cases per 100 000 population (average 1466 /100 000, ie, 40.0% of current cases). The most impactful drivers of total protection were duration of natural immunity against influenza A, R0 and QLAIV immunity duration and efficacy. In all evaluated scenarios, there was a large direct and even larger indirect protection compared with the reference scenario. Conclusions: The model highlights direct and indirect protection benefits when vaccinating healthy children with QLAIV in Europe, across a range of demographic structures, contact patterns and vaccination coverage rates.

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.

Is the impact of childhood influenza vaccination less than expected: a transmission modelling study

BACKGROUND

To reduce the burden of severe influenza, most industrialized countries target specific risk-groups with influenza vaccines, e.g. the elderly or individuals with comorbidities. Since children are the main spreaders, some countries have recently implemented childhood vaccination programs to reduce overall virus transmission and thereby influenza disease in the whole population. The introduction of childhood vaccination programs was often supported by modelling studies that predicted substantial incidence reductions. We developed a mathematical transmission model to examine the potential impact of childhood influenza vaccination in Germany, while also challenging established modelling assumptions.

METHODS

We developed an age-stratified SEIR-type transmission model to reproduce the epidemic influenza seasons between 2003/04 and 2013/14. The model was built upon German population counts, contact patterns, and vaccination history and was fitted to seasonal data on influenza-attributable medically attended acute respiratory infections (I-MAARI) and strain distribution using Bayesian methods. As novelties we (i) implemented a stratified model structure enabling seasonal variability and (ii) deviated from the commonly assumed mass-action-principle by employing a phenomenological transmission rate.

RESULTS

According to the model, by vaccinating primarily the elderly over ten seasons 4 million (95% prediction interval: 3.84 - 4.19) I-MAARI were prevented which corresponds to an 8.6% (8.3% - 8.9%) reduction compared to a no-vaccination scenario and a number-needed-to-vaccinate (NNV) to prevent one I-MAARI of 37.1 (35.5 - 38.7). Additional vaccination of 2-10 year-old children at 40% coverage would have led to an overall I-MAARI reduction of 17.8% (17.1 - 18.7%) mostly due to indirect effects with a NNV of 20.7 (19.6 - 21.6). When employing the traditional mass-action-principle, the model predicted a more than 3-fold higher I-MAARI reduction (55.6%) due to childhood vaccination.

CONCLUSION

In Germany, the introduction of routine childhood influenza vaccination could considerably reduce I-MAARI among all age-groups and improve the NNV. However, the predicted impact is much lower compared to previous studies, which is primarily caused by our phenomenological approach to modelling influenza virus transmission.

Hemagglutination inhibiting antibody persistence 1 year after influenza vaccination in Korean children and adolescents

This study aimed to assess the 1-y immunogenicity of influenza vaccines and the association between immunogenicity at 1 m and further influenza infections in children aged 6 m to 18 y. Serum hemagglutination inhibition (HI) antibody titers and GMTs were determined for the recommended influenza strains 0, 1, 6, and 12 m post-vaccination. The serological evidence of influenza infections were defined as the increase of HI titer (HI ≥1:40 and 4-fold rise). The seroprotection rates for strains A(H1N1), A(H3N2), and B were 91.2%, 87.6%, and 87.6%, respectively, at 1 month (n = 174). These rates were 76.5%, 64.7%, and 54.6%, respectively, at 12 m. The seroprotection rates and GMTs for influenza A(H1N1) and A(H3N2) were higher at 12 m than at 0 m (p < 0.05) but not for B. There were 39 subjects (42 cases) of serological influenza infections. Subjects with seroprotection at 1 m post-vaccination had showed fewer serologic A(H1N1) (10.1 vs 54.5%) and A(H3N2) (7.2 vs 38.1%) infections than the ones with HI titer <1:40 during follow-up (P < 0.01). In conclusion, influenza vaccines used during the 2008-09 season induced adequate 1-y immunogenicity for A(H1N1) and A(H3N2). The immunogenicity at one month after vaccination influenced further serological influenza infections.

Assessment of Public Health and Economic Impact of Intranasal Live-Attenuated Influenza Vaccination of Children in France Using a Dynamic Transmission Model

OBJECTIVES

We estimated the epidemiological and economic impact of extending the French influenza vaccination programme from at-risk/elderly (≥65 years) only to healthy children (2-17 years).

METHODS

A deterministic, age-structured, dynamic transmission model was used to simulate the transmission of influenza in the French population, using the current vaccination coverage with trivalent inactivated vaccine (TIV) in at-risk/elderly individuals (current strategy) or gradually extending the vaccination to healthy children (aged 2-17 years) with intranasal, quadrivalent live-attenuated influenza vaccine (QLAIV) from current uptake up to 50% (evaluated strategy). Epidemiological, medical resource use and cost data were taken from international literature and country-specific information. The model was calibrated to the observed numbers of influenza-like illness visits/year. The 10-year number of symptomatic cases of confirmed influenza and direct medical costs ('all-payer') were calculated for the 0-17- (direct and indirect effects) and ≥18-year-old (indirect effect). The incremental cost-effectiveness ratio (ICER) was calculated for the total population, using a 4% discount rate/year.

RESULTS

Assuming 2.3 million visits/year and 1960 deaths/year, the model calibration yielded an all-year average basic reproduction number (R ₀) of 1.27. In the population aged 0-17 years, QLAIV prevented 865,000 influenza cases/year (58.4%), preventing 10-year direct medical expenses of €374 million. In those aged ≥18 years with unchanged TIV coverage, 1.2 million cases/year were averted (27.6%) via indirect effects (additionally prevented expenses, €457 million). On average, 613 influenza-related deaths were averted annually overall. The ICER was €18,001/life-year gained. The evaluated strategy had a 98% probability of being cost-effective at a €31,000/life-year gained threshold.

CONCLUSIONS

The model demonstrated strong direct and indirect benefits of protecting healthy children against influenza with QLAIV on public health and economic outcomes in France.

Cost-effectiveness of seasonal quadrivalent versus trivalent influenza vaccination in the United States: A dynamic transmission modeling approach

Trivalent inactivated influenza vaccines (IIV3s) protect against 2 A strains and one B lineage; quadrivalent versions (IIV4s) protect against an additional B lineage. The objective was to assess projected health and economic outcomes associated with IIV4 versus IIV3 for preventing seasonal influenza in the US. A cost-effectiveness model was developed to interact with a dynamic transmission model. The transmission model tracked vaccination, influenza cases, infection-spreading interactions, and recovery over 10 y (2012–2022). The cost-effectiveness model estimated influenza-related complications, direct and indirect costs (2013–2014 US$), health outcomes, and cost-effectiveness. Inputs were taken from published/public sources or estimated using regression or calibration. Outcomes were discounted at 3% per year. Scenario analyses tested the reliability of the results. Seasonal vaccination with IIV4 versus IIV3 is predicted to reduce annual influenza cases by 1,973,849 (discounted; 2,325,644 undiscounted), resulting in 12–13% fewer cases and influenza-related complications and deaths. These reductions are predicted to translate into 18,485 more quality-adjusted life years (QALYs) accrued annually for IIV4 versus IIV3. Increased vaccine-related costs ($599 million; 5.7%) are predicted to be more than offset by reduced influenza treatment costs ($699 million; 12.2%), resulting in direct medical cost saving annually ($100 million; 0.6%). Including indirect costs, savings with IIV4 are predicted to be $7.1 billion (5.6%). Scenario analyses predict IIV4 to be cost-saving in all scenarios tested apart from low infectivity, where IIV4 is predicted to be cost-effective. In summary, seasonal influenza vaccination in the US with IIV4 versus IIV3 is predicted to improve health outcomes and reduce costs.

Cost-effectiveness analysis of quadrivalent versus trivalent influenza vaccine in Taiwan: A lifetime multi-cohort model

A government-funded trivalent influenza vaccine (TIV) program to prevent seasonal influenza was implemented in Taiwan since 1998. However, mismatch between the vaccine and circulating strains may occur. Alternatively, a quadrivalent influenza vaccine (QIV) includes all 4 influenza lineages could minimize the risk of mismatches. Therefore, QIV could be considered as an alternative strategy to enhance protection against seasonal influenza. The objective of the study was to analyze, from a governmental perspective, the cost-effectiveness of using QIV vs. TIV as a vaccination strategy in Taiwan. A lifetime multi-cohort, static Markov model was constructed with 9 age groups to assess the costs and effectiveness of QIV vs. TIV. Direct costs were obtained from a database released by the Ministry of Health and Welfare. Outcomes included life-years gained, quality-adjusted life years (QALYs) gained, influenza cases avoided and incremental cost-effectiveness ratios (ICERs). The discount rate of costs and effectiveness was set at 3.5% and the time horizon used in the model was 100 y. Results show that a vaccination strategy utilizing QIV instead of TIV would bring an additional 10,557 QALYs at an extra cost of US$39.4 million, yielding an ICER of US$3,015.07 per QALY gained. When setting the willingness-to-pay threshold at US$10,000, compared to TIV, the probability that QIV would be cost-effective was 98%. Sensitivity analyses show that ICER was sensitive to the changes of circulation of influenza virus subtypes and vaccine mismatch. From a governmental perspective, the QIV vaccination could be considered as a cost-effective strategy within the context of public health in Taiwan.

Estimates of the Public Health Impact of a Pediatric Vaccination Program Using an Intranasal Tetravalent Live-Attenuated Influenza Vaccine in Belgium

OBJECTIVES

Our objectives were to estimate the public health outcomes of vaccinating Belgian children using an intranasal tetravalent live-attenuated influenza vaccine (QLAIV) combined with current coverage of high-risk/elderly individuals using the trivalent inactivated vaccine.

METHODS

We used a deterministic, age-structured, dynamic model to simulate seasonal influenza transmission in the Belgian population under the current coverage or after extending vaccination with QLAIV to healthy children aged 2-17 years. Differential equations describe demographic changes, exposure to infectious individuals, infection recovery, and immunity dynamics. The basic reproduction number (R 0) was calibrated to the observed number of influenza doctor visits/year. Vaccine efficacy was 80 % (live-attenuated) and 59-68 % (inactivated). The 10-year incidence of symptomatic influenza was calculated with different coverage scenarios (add-on to current coverage).

RESULTS

Model calibration yielded R 0 = 1.1. QLAIV coverage of 75 % of those aged 2-17 years averted 374,000 symptomatic cases/year (57 % of the current number), 244,000 of which were among adults (indirect effect). Vaccinating 75 % of those aged 2-11 years and 50 % of those aged 12-17 years averted 333,200 cases/year (213,000 adult cases/year). Vaccinating only healthy children aged 2-5 years generated direct protection but limited indirect protection, even with 90 % coverage (40,800 averted adult cases/year; -8.4 %). Targeting all children averted twice as many high-risk cases as targeting high-risk children only (8485 vs. 4965/year with 75 % coverage). Sensitivity analyses showed the robustness of results.

CONCLUSIONS

The model highlights the direct and indirect protection benefits when vaccinating healthy children with QLAIV in Belgium. Policies targeting only high-risk individuals or the youngest provide limited herd protection, as school-age children are important influenza vectors in the community.

Seasonal influenza vaccine policy, use and effectiveness in the tropics and subtropics - a systematic literature review

AIM

The evidence needed for tropical countries to take informed decisions on influenza vaccination is scarce. This article reviews policy, availability, use and effectiveness of seasonal influenza vaccine in tropical and subtropical countries.

METHOD

Global health databases were searched in three thematic areas - policy, availability and protective benefits in the context of human seasonal influenza vaccine in the tropics and subtropics. We excluded studies on monovalent pandemic influenza vaccine, vaccine safety, immunogenicity and uptake, and disease burden.

RESULTS

Seventy-four countries in the tropics and subtropics representing 60% of the world's population did not have a national vaccination policy against seasonal influenza. Thirty-eight countries used the Northern Hemisphere and 21 countries the Southern Hemisphere formulation. Forty-six countries targeted children and 57 targeted the elderly; though, the age cut-offs varied. Influenza vaccine supply increased twofold in recent years. However, coverage remained lower than five per 1000 population. Vaccine protection against laboratory-confirmed influenza in the tropics ranged from 0% to 42% in the elderly, 20-77% in children and 50-59% in healthy adults. Vaccinating pregnant women against seasonal influenza prevented laboratory-confirmed influenza in both mothers (50%) and their infants <6 months (49-63%).

CONCLUSION

Guidelines on vaccine composition, priority risk groups and vaccine availability varied widely. The evidence on vaccine protection was scarce. Countries in the tropics and subtropics need to strengthen and expand their evidence-base required for making informed decisions on influenza vaccine introduction and expansion, and how much benefit to expect.

Public health and economic impact of seasonal influenza vaccination with quadrivalent influenza vaccines compared to trivalent influenza vaccines in Europe

Influenza B strains represent on average 23% of all circulating strains in Europe and when there is a vaccine mismatch on B strains, additional influenza-related hospitalizations and deaths as well as substantial additional costs are observed. The objective was to estimate the public health and economic impact of seasonal influenza vaccination with quadrivalent influenza vaccines (QIV) compared to trivalent influenza vaccines (TIV) in Europe (EU).

Based on data from 5 EU countries (France, Germany, Italy, Spain and UK) during 10 influenza seasons from 2002 to 2013, epidemiological and associated economic outcomes were estimated for each season for the actual scenario where the TIV was used, and for a hypothetical scenario where QIV could have been used instead.

By using QIV, this study estimated that for the 5 EU countries, an additional 1.03 million (327.9/100,000 inhabitants) influenza cases, 453,000 (143.9/100,000) general practitioners consultations, 672,000 (213.1/100,000) workdays lost, 24,000 (7.7/100,000) hospitalizations and 10,000 (3.1/100,000) deaths could have been avoided compared to the use of TIV over the 10-seasons-period. This study estimates that QIV can be of economic value since from a societal perspective 15 million Euros would have been saved on general practitioners consultations (14 million Euros from third-party payer perspective), 77 million on hospitalizations (74 million Euros from third-party payer perspective) and 150 million Euros on workdays lost, across the 5 EU countries.

In conclusion, the present study estimates that, compared to TIV, QIV may result in a substantial decrease in epidemiological burden and in influenza-related costs.

Effectiveness of influenza vaccination for preventing influenza-related complications in people with asthma: a systematic review protocol

INTRODUCTION

Influenza vaccination is administered annually as a preventive measure against influenza infection and influenza-related complications in high-risk individuals, such as those with asthma. However, the effectiveness of influenza vaccination in people with asthma against influenza-related complications is still not well established.

METHODS AND ANALYSIS

We will search the following databases: MEDLINE (Ovid), EMBASE (Ovid), Cumulative Index to Nursing and Allied Health Literature (CINAHL), Cochrane Central Register of Controlled Trials (CENTRAL), Scopus, Cochrane Database of Systematic Reviews (CDSR), Web of Science Core Collection, Science direct, WHO Library Information System (WHOLIS), Global Health Library and Chinese databases (CNKI, Wanfang and ChongQing VIP) from Jan 1970 to Jan 2016 for observational and experimental studies on effectiveness of influenza vaccine in people with asthma. The identification of studies will be complemented with the searching of the reference lists and citations, and contacting influenza vaccine manufacturers to identify unpublished or ongoing studies. Two reviewers will extract data and appraise the quality of each study independently. Separate meta-analyses will be undertaken for observational and experimental evidence using fixed-effect or random-effects models, as appropriate.

ETHICS AND DISSEMINATION

Formal ethical approval is not required, as primary data will not be collected. The review will be disseminated in peer-reviewed publications and conference presentations.

Systems biology of immunity to MF59-adjuvanted versus nonadjuvanted trivalent seasonal influenza vaccines in early childhood

The dynamics and molecular mechanisms underlying vaccine immunity in early childhood remain poorly understood. Here we applied systems approaches to investigate the innate and adaptive responses to trivalent inactivated influenza vaccine (TIV) and MF59-adjuvanted TIV (ATIV) in 90 14- to 24-mo-old healthy children. MF59 enhanced the magnitude and kinetics of serum antibody titers following vaccination, and induced a greater frequency of vaccine specific, multicytokine-producing CD4(+) T cells. Compared with transcriptional responses to TIV vaccination previously reported in adults, responses to TIV in infants were markedly attenuated, limited to genes regulating antiviral and antigen presentation pathways, and observed only in a subset of vaccinees. In contrast, transcriptional responses to ATIV boost were more homogenous and robust. Interestingly, a day 1 gene signature characteristic of the innate response (antiviral IFN genes, dendritic cell, and monocyte responses) correlated with hemagglutination at day 28. These findings demonstrate that MF59 enhances the magnitude, kinetics, and consistency of the innate and adaptive response to vaccination with the seasonal influenza vaccine during early childhood, and identify potential molecular correlates of antibody responses.

Hygiene Behaviors Associated with Influenza-Like Illness among Adults in Beijing, China: A Large, Population-Based Survey

The objective of this study was to identify possible hygiene behaviors associated with the incidence of ILI among adults in Beijing. In January 2011, we conducted a multi-stage sampling, cross-sectional survey of adults living in Beijing using self-administered anonymous questionnaires. The main outcome variable was self-reported ILI within the past year. Multivariate logistic regression was used to identify factors associated with self-reported ILI. A total of 13003 participants completed the questionnaires. 6068 (46.7%) of all participants reported ILI during the past year. After adjusting for demographic characteristics, the variables significantly associated with a lower likelihood of reporting ILI were regular physical exercise (OR 0.80; 95% CI 0.74–0.87), optimal hand hygiene (OR 0.87; 95% CI 0.80–0.94), face mask use when going to hospitals (OR 0.87; 95% CI 0.80–0.95), and not sharing of towels and handkerchiefs (OR 0.68; 95% CI 0.63–0.73). These results highlight that personal hygiene behaviors were potential preventive factors against the incidence of ILI among adults in Beijing, and future interventions to improve personal hygiene behaviors are needed in Beijing.

Cost-effectiveness evaluation of quadrivalent influenza vaccines for seasonal influenza prevention: a dynamic modeling study of Canada and the United Kingdom

Background

The adoption of quadrivalent influenza vaccine (QIV) to replace trivalent influenza vaccine (TIV) in immunization programs is growing worldwide, thus helping to address the problem of influenza B lineage mismatch. However, the price per dose of QIV is higher than that of TIV. In such circumstances, cost-effectiveness analyses provide important and relevant information to inform national health recommendations and implementation decisions. This analysis assessed potential vaccine impacts and cost-effectiveness of a country-wide switch from TIV to QIV, in Canada and the UK, from a third-party payer perspective.

Methods

An age-stratified, dynamic four-strain transmission model which incorporates strain interaction, transmission-rate seasonality and age-specific mixing in the population was used. Model input data were obtained from published literature and online databases. In Canada, we evaluated a switch from TIV to QIV in the entire population. For the UK, we considered two strategies: Children aged 2–17 years who receive the live-attenuated influenza vaccine (LAIV) switch to the quadrivalent formulation (QLAIV), while individuals aged > 18 years switch from TIV to QIV. Two different vaccination uptake scenarios in children (UK1 and UK2, which differ in the vaccine uptake level) were considered. Health and cost outcomes for both vaccination strategies, and the cost-effectiveness of switching from TIV/LAIV to QIV/QLAIV, were estimated from the payer perspective. For Canada and the UK, cost and outcomes were discounted using 5 % and 3.5 % per year, respectively.

Results

Overall, in an average influenza season, our model predicts that a nationwide switch from TIV to QIV would prevent 4.6 % influenza cases, 4.9 % general practitioner (GP) visits, 5.7 % each of emergency room (ER) visits and hospitalizations, and 6.8 % deaths in Canada. In the UK (UK1/UK2), implementing QIV would prevent 1.4 %/1.8 % of influenza cases, 1.6 %/2.0 % each of GP and ER visits, 1.5 %/1.9 % of hospitalizations and 4.3 %/4.9 % of deaths. Discounted incremental cost-utility ratios of $7,961 and £7,989/£7,234 per quality-adjusted life-year (QALY) gained are estimated for Canada and the UK (UK1/UK2), both of which are well within their respective cost-effectiveness threshold values.

Conclusions

Switching from TIV to QIV is expected to be a cost-effective strategy to further reduce the burden of influenza in both countries.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-015-1193-4) contains supplementary material, which is available to authorized users.

Advax delta inulin adjuvant overcomes immune immaturity in neonatal mice thereby allowing single-dose influenza vaccine protection

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A single dose of Advax-adjuvanted influenza vaccine in 7-day-old pups protected against lethal influenza infection.

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Advax adjuvant enhanced both B-cell and T-cell memory in neonates.

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Influenza protection in Advax-immunized neonates was dependent on memory B-cells.

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Advax adjuvant confirmed to be safe and well tolerated in neonates.

Neonates are at high risk for influenza morbidity and mortality due to immune immaturity and lack of priming by prior influenza virus exposure. Inactivated influenza vaccines are ineffective in infants under six months and to provide protection in older children generally require two doses given a month apart. This leaves few options for rapid protection of infants, e.g. during an influenza pandemic. We investigated whether Advax™, a novel polysaccharide adjuvant based on delta inulin microparticles could help overcome neonatal immune hypo-responsiveness. We first tested whether it was possible to use Advax to obtain single-dose vaccine protection of neonatal pups against lethal influenza infection. Inactivated influenza A/H1N1 vaccine (iH1N1) combined with Advax™ adjuvant administered as a single subcutaneous immunization to 7-day-old mouse pups significantly enhanced serum influenza-specific IgM, IgG1, IgG2a and IgG2b levels and was associated with a 3–4 fold increase in the frequency of splenic influenza-specific IgM and IgG antibody secreting cells. Pups immunized with Advax had significantly higher splenocyte influenza-stimulated IFN-γ, IL-2, IL-4, and IL-10 production by CBA and a 3–10 fold higher frequency of IFN-γ, IL-2, IL-4 or IL-17 secreting T cells by ELISPOT. Immunization with iH1N1 + Advax induced robust protection of pups against virus challenge 3 weeks later, whereas pups immunized with iH1N1 antigen alone had no protection. Protection by Advax-adjuvanted iH1N1 was dependent on memory B cells rather than memory T cells, with no protection in neonatal μMT mice that are B-cell deficient. Hence, Advax adjuvant overcame neonatal immune hypo-responsiveness and enabled single-dose protection of pups against otherwise lethal influenza infection, thereby supporting ongoing development of Advax™ as a neonatal vaccine adjuvant.

Restricted replication of the live attenuated influenza A virus vaccine during infection of primary differentiated human nasal epithelial cells

Live Attenuated Influenza Vaccine (LAIV) strains are associated with cold adapted, temperature sensitive and attenuated phenotypes that have been studied in non-human or immortalized cell cultures as well as in animal models. Using a primary, differentiated human nasal epithelial cell (hNEC) culture system we compared the replication kinetics, levels of cell-associated viral proteins and virus particle release during infection with LAIV or the corresponding wild type (WT) influenza viruses. At both 33 °C and 37 °C, seasonal influenza virus and an antigenically matched LAIV replicated to similar titers in MDCK cells but seasonal influenza virus replicated to higher titers than LAIV in hNEC cultures, suggesting a greater restriction of LAIV replication in hNEC cultures. Despite the disparity in infectious virus production, the supernatants from H1N1 and LAIV infected hNEC cultures had equivalent amounts of viral proteins and hemagglutination titers, suggesting the formation of non-infectious virus particles by LAIV in hNEC cultures.

Protection against Influenza A Virus Challenge with M2e-Displaying Filamentous Escherichia coli Phages

Human influenza viruses are responsible for annual epidemics and occasional pandemics that cause severe illness and mortality in all age groups worldwide. Matrix protein 2 (M2) of influenza A virus is a tetrameric type III membrane protein that functions as a proton-selective channel. The extracellular domain of M2 (M2e) is conserved in human and avian influenza A viruses and is being pursued as a component for a universal influenza A vaccine. To develop a M2e vaccine that is economical and easy to purify, we genetically fused M2e amino acids 2-16 to the N-terminus of pVIII, the major coat protein of filamentous bacteriophage f88. We show that the resulting recombinant f88-M2e2-16 phages are replication competent and display the introduced part of M2e on the phage surface. Immunization of mice with purified f88-M2e2-16 phages in the presence of incomplete Freund's adjuvant, induced robust M2e-specific serum IgG and protected BALB/c mice against challenge with human and avian influenza A viruses. Thus, replication competent filamentous bacteriophages can be used as efficient and economical carriers to display conserved B cell epitopes of influenza A.

Influenza Vaccination Strategies: Comparing Inactivated and Live Attenuated Influenza Vaccines

Influenza is a major respiratory pathogen causing annual outbreaks and occasional pandemics. Influenza vaccination is the major method of prophylaxis. Currently annual influenza vaccination is recommended for groups at high risk of complications from influenza infection such as pregnant women, young children, people with underlying disease and the elderly, along with occupational groups such a healthcare workers and farm workers. There are two main types of vaccines available: the parenteral inactivated influenza vaccine and the intranasal live attenuated influenza vaccine. The inactivated vaccines are licensed from 6 months of age and have been used for more than 50 years with a good safety profile. Inactivated vaccines are standardized according to the presence of the viral major surface glycoprotein hemagglutinin and protection is mediated by the induction of vaccine strain specific antibody responses. In contrast, the live attenuated vaccines are licensed in Europe for children from 2-17 years of age and provide a multifaceted immune response with local and systemic antibody and T cell responses but with no clear correlate of protection. Here we discuss the immunological immune responses elicited by the two vaccines and discuss future work to better define correlates of protection.

Measuring Cellular Immunity to Influenza: Methods of Detection, Applications and Challenges

Influenza A virus is a respiratory pathogen which causes both seasonal epidemics and occasional pandemics; infection continues to be a significant cause of mortality worldwide. Current influenza vaccines principally stimulate humoral immune responses that are largely directed towards the variant surface antigens of influenza. Vaccination can result in an effective, albeit strain-specific antibody response and there is a need for vaccines that can provide superior, long-lasting immunity to influenza. Vaccination approaches targeting conserved viral antigens have the potential to provide broadly cross-reactive, heterosubtypic immunity to diverse influenza viruses. However, the field lacks consensus on the correlates of protection for cellular immunity in reducing severe influenza infection, transmission or disease outcome. Furthermore, unlike serological methods such as the standardized haemagglutination inhibition assay, there remains a large degree of variation in both the types of assays and method of reporting cellular outputs. T-cell directed immunity has long been known to play a role in ameliorating the severity and/or duration of influenza infection, but the precise phenotype, magnitude and longevity of the requisite protective response is unclear. In order to progress the development of universal influenza vaccines, it is critical to standardize assays across sites to facilitate direct comparisons between clinical trials.

Vaccination in the elderly: what can be recommended?

The age-associated increased susceptibility to infectious disease would suggest that vaccination should be a route to promote healthy aging and keep our seniors autonomous and independent. While vaccination represents a cost-effective and efficient strategy at community level, the ability of the immune system to mount a protective immune response is still unpredictable at the level of the individual. Thus, at a similar age, some individuals, including the elderly, might still be 'good' responders while some other, even younger, would definitely fail to mount a protective response. In this review, the current burden of vaccine-preventable diseases in the aging and aged population will be detailed with the aim to identify the ideal vaccine candidates over the age of 50 years. This article will conclude with potential strategies to reduce, as best as possible, this burden and the imperative need to overcome barriers in extending current vaccine coverage towards to a lifelong vaccine schedule.

Effectiveness of influenza vaccination programme in preventing hospital admissions, Valencia, 2014/15 early results

Preliminary results for the 2014/15 season indicate low to null effect of vaccination against influenza A(H3N2)-related disease. As of week 5 2015, there have been 1,136 hospital admissions, 210 were due to influenza and 98% of subtype A strains were H3. Adjusted influenza vaccine effectiveness was 33% (range: 6-53%) overall and 40% (range: 13% to 59%) in those 65 years and older. Vaccination reduced by 44% (28-68%) the probability of admission with influenza.

Evidence-based management of otitis media: a 5S model approach

Objective:

The 5S model proposes five hierarchical levels (systems, summaries, synopses, syntheses and studies) of pre-appraised evidence to guide evidence-based practice. This review aimed to identify and summarise pre-appraised evidence at the highest available 5S level for the management of different subsets of otitis media: acute otitis media, otitis media with effusion, chronic suppurative otitis media and cholesteatoma in both adults and children.

Method:

Data sources were pre-appraised evidence resources. Evidence freely available from sources at the highest available level of the 5S model were summarised for this review.

Results:

System level evidence exists for acute otitis media and otitis media with effusion. Summary level evidence exists for recurrent acute otitis media and medical management of chronic suppurative otitis media. There is an absence of randomised controlled trials to prove the efficacy of surgical management of chronic suppurative otitis media and cholesteatoma.

Conclusion:

Until randomised controlled trial data are generated, consensus publications on the surgical management of chronic suppurative otitis media and cholesteatoma should be used to guide best practice.

Adenoviral vectors as novel vaccines for influenza

OBJECTIVES

Influenza is a viral respiratory disease causing seasonal epidemics, with significant annual illness and mortality. Emerging viruses can pose a major pandemic threat if they acquire the capacity for sustained human-to-human transmission. Vaccination reduces influenza-associated mortality and is critical in minimising the burden on the healthcare system. However, current vaccines are not always effective in at-risk populations and fail to induce long-lasting protective immunity against a range of viruses.

KEY FINDINGS

The development of 'universal' influenza vaccines, which induce heterosubtypic immunity capable of reducing disease severity, limiting viral shedding or protecting against influenza subtypes with pandemic potential, has gained interest in the research community. To date, approaches have focused on inducing immune responses to conserved epitopes within the stem of haemagglutinin, targeting the ectodomain of influenza M2e or by stimulating cellular immunity to conserved internal antigens, nucleoprotein or matrix protein 1.

SUMMARY

Adenoviral vectors are potent inducers of T-cell and antibody responses and have demonstrated safety in clinical applications, making them an excellent choice of vector for delivery of vaccine antigens. In order to circumvent pre-existing immunity in humans, serotypes from non-human primates have recently been investigated. We will discuss the pre-clinical development of these novel vectors and their advancement to clinical trials.

Estimating influenza vaccine effectiveness using routine surveillance data among children aged 6-59 months for five consecutive influenza seasons

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Multiyear studies are preferred for estimating robust influenza vaccine effectiveness over time.

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An efficient way to evaluate the influenza vaccine effectiveness was used, through data linkage of two already established systems in the public health sector.

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We applied both fixed-effects and random-effects meta-analysis of case–control studies to estimate the pooled vaccine effectiveness for children aged 6–59 months across five influenza seasons and considered the variation in antigenic match and epidemics year by year as the heterogeneity between studies.

Objectives

We aimed to estimate the pooled vaccine effectiveness (VE) in children over five winters through data linkage of two existing surveillance systems.

Methods

Five test-negative case–control studies were conducted from November to February during the 2004/2005 to 2008/2009 seasons. Sentinel physicians from the Viral Surveillance Network enrolled children aged 6–59 months with influenza-like illness to collect throat swabs. Through linking with a nationwide vaccination registry, we measured the VE with a logistic regression model adjusting for age, gender, and week of symptom onset. Both fixed-effects and random-effects models were used in the meta-analysis.

Results

Four thousand four hundred and ninety-four subjects were included. The proportion of influenza test-positive subjects across the five seasons was 11.5% (132/1151), 7.2% (41/572), 23.9% (189/791), 6.6% (75/1135), and 11.2% (95/845), respectively. The pooled VE was 62% (95% confidence interval (CI) 48–83%) in both meta-analysis models. By age category, VE was 51% (95% CI 23–68%) for those aged 6–23 months and 75% (95% CI 60–84%) for those aged 24–59 months.

Conclusions

Influenza vaccination provided measurable protection against laboratory-confirmed influenza among children aged 6–59 months despite variations in the vaccine match during the 2004/2005 to 2008/2009 influenza seasons in Taiwan.

Enhanced and persistent antibody response against homologous and heterologous strains elicited by a MF59-adjuvanted influenza vaccine in infants and young children

BACKGROUND

Non-adjuvanted seasonal influenza vaccines show only modest efficacy in young children. This study compared the immunogenicity, reactogenicity and safety of the MF59-adjuvanted trivalent subunit vaccine (aTIV) with two non-adjuvanted trivalent vaccines, TIV-1, the non-adjuvanted version of aTIV, and TIV-2, a split virion vaccine.

METHODS

6078 children received two doses of aTIV (n=3125), TIV-1 (n=1479), or TIV-2 (n=1474) four weeks apart (Days 1 and 29). Children aged 6 to <36 months and 36 to <72 months received 0.25 mL and 0.50 mL doses, respectively. Immunogenicity was assessed by hemagglutination inhibition (HI) assay (n=2435) on Days 1, 29, 50 and 209. Safety was assessed up to Day 394.

RESULTS

After the second vaccination (Day 50), the aTIV group showed significantly higher geometric mean HI titers and seroconversion rates than the TIV-1 or TIV-2 groups against all homologous and heterologous strains. The difference was enhanced at HI titers ≥110. aTIV elicited a faster, more persistent antibody response, with significantly higher titers in the aTIV group after one vaccination (Day 29) and after six months (Day 209) than in either TIV group. aTIV was more reactogenic than were TIV-1 and TIV-2 but rates of severe adverse events were very low for all three vaccines.

CONCLUSION

In infants and young children, the MF59-adjuvanted vaccine induced substantially faster (after one dose), higher, persistent HI titers than the non-adjuvanted vaccines, with consistently higher seroprotection rates at increased threshold HI titers. This trial is registered at clinicaltrials.gov: NCT01346592.

The potential cost-effectiveness of quadrivalent versus trivalent influenza vaccine in elderly people and clinical risk groups in the UK: a lifetime multi-cohort model

OBJECTIVE

To estimate the potential cost-effectiveness of quadrivalent influenza vaccine compared with trivalent influenza vaccine in the UK.

METHODS

A lifetime, multi-cohort, static Markov model was constructed, with nine age groups each divided into healthy and at-risk categories. Influenza A and B were accounted for separately. The model was run in one-year cycles for a lifetime (maximum age: 100 years). The analysis was from the perspective of the UK National Health Service. Costs and benefits were discounted at 3.5%. 2010 UK vaccination policy (vaccination of people at risk and those aged ≥65 years) was applied. Herd effect was not included. Inputs were derived from national databases and published sources where possible. The quadrivalent influenza vaccine price was not available when the study was conducted. It was estimated at £6.72,15% above the trivalent vaccine price of £5.85. Sensitivity analyses used an incremental price of up to 50%.

RESULTS

Compared with trivalent influenza vaccine, the quadrivalent influenza vaccine would be expected to reduce the numbers of influenza cases by 1,393,720, medical visits by 439,852 complications by 167,357, hospitalisations for complications by 26,424 and influenza deaths by 16,471. The estimated base case incremental cost-effectiveness ratio (ICER) was £5,299/quality-adjusted life-year (QALY). Sensitivity analyses indicated that the ICER was sensitive to changes in circulation of influenza virus subtypes and vaccine mismatch; all other parameters had little effect. In 96% of simulations the ICER was <£20,000/QALY. Since this analysis was completed, quadrivalent influenza vaccine has become available in the UK at a list price of £9.94. Using this price in the model, the estimated ICER for quadrivalent compared with trivalent vaccination was £27,378/QALY, still within the NICE cost-effectiveness threshold (£20,000-£30,000).

CONCLUSIONS

Quadrivalent influenza vaccine could reduce influenza disease burden and would be cost-effective compared with trivalent influenza vaccine in elderly people and clinical risk groups in the UK.

Understanding knowledge, attitudes, and behaviors related to influenza and the influenza vaccine in US-Mexico border communities

Hispanics are less likely to receive the influenza vaccine compared to other racial and ethnic groups in the US. Hispanic residents of the US-Mexico border region may have differing health beliefs and behaviors, and their cross-border mobility impacts disease control. To assess beliefs and behaviors regarding influenza prevention and control among border populations, surveys were conducted at border clinics. Of 197 respondents, 34 % reported conditions for which vaccination is indicated, and travel to Mexico was common. Few (35 %) believed influenza could make them 'very sick', and 76 % believed they should take antibiotics to treat influenza. Influenza vaccine awareness was high, and considered important, but only 36 % reported recent vaccination. The belief that influenza vaccination is 'very important' was strongly associated with recent vaccination; "Didn't think about it" was the most common reason for being un-vaccinated. Misconceptions about influenza risk, prevention and treatment were common in this Hispanic border population; improved educational efforts and reminder systems could impact vaccination behaviors.

The effectiveness of seasonal trivalent inactivated influenza vaccine in preventing laboratory confirmed influenza hospitalisations in Auckland, New Zealand in 2012

BACKGROUND

Few studies report the effectiveness of trivalent inactivated influenza vaccine (TIV) in preventing hospitalisation for influenza-confirmed respiratory infections. Using a prospective surveillance platform, this study reports the first such estimate from a well-defined ethnically diverse population in New Zealand (NZ).

METHODS

A case test-negative design was used to estimate propensity adjusted vaccine effectiveness. Patients with a severe acute respiratory infection (SARI), defined as a patient of any age requiring hospitalisation with a history of a fever or a measured temperature ≥38°C and cough and onset within the past 7 days, admitted to public hospitals in South and Central Auckland were eligible for inclusion in the study. Cases were SARI patients who tested positive for influenza, while non-cases (controls) were SARI patients who tested negative. Results were adjusted for the propensity to be vaccinated and the timing of the influenza season.

RESULTS

The propensity and season adjusted vaccine effectiveness (VE) was estimated as 39% (95% CI 16;56). The VE point estimate against influenza A (H1N1) was lower than for influenza B or influenza A (H3N2) but confidence intervals were wide and overlapping. Estimated VE was 59% (95% CI 26;77) in patients aged 45-64 years but only 8% (-78;53) in those aged 65 years and above.

CONCLUSION

Prospective surveillance for SARI has been successfully established in NZ. This study for the first year, the 2012 influenza season, has shown low to moderate protection by TIV against influenza positive hospitalisation.

Relative efficacy of AS03-adjuvanted pandemic influenza A(H1N1) vaccine in children: results of a controlled, randomized efficacy trial

Background. The vaccine efficacy (VE) of 1 or 2 doses of AS03-adjuvanted influenza A(H1N1) vaccine relative to that of 2 doses of nonadjuvanted influenza A(H1N1) vaccine in children 6 months to <10 years of age in a multinational study conducted during 2010–2011.

Methods. A total of 6145 children were randomly assigned at a ratio of 1:1:1 to receive 2 injections 21 days apart of A/California/7/2009(H1N1)-AS03 vaccine at dose 1 and saline placebo at dose 2, 2 doses 21 days apart of A/California/7/2009(H1N1)-AS03 vaccine (the Ad2 group), or 2 doses 21 days apart of nonadjuvanted A/California/7/2009(H1N1) vaccine (the NAd2 group). Active surveillance for influenza-like illnesses continued from days 14 to 385. Nose and throat samples obtained during influenza-like illnesses were tested for A/California/7/2009(H1N1), using reverse-transcriptase polymerase chain reaction. Immunogenicity, reactogenicity, and safety were assessed.

Results. There were 23 cases of confirmed 2009 pandemic influenza A(H1N1) (A[H1N1]pdm09) infection for the primary relative VE analysis. The VE in the Ad2 group relative to that in the NAd2 group was 76.8% (95% confidence interval, 18.5%–93.4%). The benefit of the AS03 adjuvant was demonstrated in terms of the greater immunogenicity observed in the Ad2 group, compared with the NAd2 group.

Conclusion. The 4–8-fold antigen-sparing adjuvanted pandemic influenza vaccine demonstrated superior and clinically important prevention of A(H1N1)pdm09 infection, compared with nonadjuvanted vaccine, with no observed increase in medically attended or serious adverse events. These data support the use of adjuvanted influenza vaccines during influenza pandemics.

Clinical Trials Registration. NCT01051661.

Cost-effectiveness analysis of universal influenza vaccination with quadrivalent inactivated vaccine in the United States

To address influenza B lineage mismatch and co-circulation, several quadrivalent inactivated influenza vaccines (IIV4s) containing two type A strains and both type B lineages have recently been approved in the United States. Currently available trivalent inactivated vaccines (IIV3s) or trivalent live attenuated influenza vaccines (LAIV3s) comprise two influenza A strains and one of the two influenza B lineages that have co-circulated in the United States since 2001. The objective of this analysis was to evaluate the cost-effectiveness of a policy of universal vaccination with IIV4 vs. IIV3/LAIV3 during 1 year in the United States. On average per influenza season, IIV4 was predicted to result in 30,251 fewer influenza cases, 3512 fewer hospitalizations, 722 fewer deaths, 4812 fewer life-years lost, and 3596 fewer quality-adjusted life-years (QALYs) lost vs. IIV3/LAIV3. Using the Fluarix Quadrivalent(TM) (GlaxoSmithKline) prices and the weighted average IIV3/LAIV3 prices, the model predicts that the vaccination program costs would increase by $452.2 million, while direct medical and indirect costs would decrease by $111.6 million and $218.7 million, respectively, with IIV4. The incremental cost-effectiveness ratio (ICER) comparing IIV4 to IIV3/LAIV3 is predicted to be $90,301/QALY gained. Deterministic sensitivity analyses found that influenza B vaccine-matched and mismatched efficacies among adults aged ≥65 years had the greatest impact on the ICER. Probabilistic sensitivity analysis showed that the cost per QALY remained below $100,000 for 61% of iterations. In conclusion, vaccination with IIV4 in the US is predicted to reduce morbidity and mortality. This strategy is also predicted to be cost-effective vs. IIV3/LAIV3 at conventional willingness-to-pay thresholds.

Differences in antibody responses between trivalent inactivated influenza vaccine and live attenuated influenza vaccine correlate with the kinetics and magnitude of interferon signaling in children

BACKGROUND

Live attenuated influenza vaccine (LAIV) and trivalent inactivated influenza vaccine (TIV) are effective for prevention of influenza virus infection in children, but the mechanisms associated with protection are not well defined.

METHODS

We analyzed the differences in B-cell responses and transcriptional profiles in children aged 6 months to 14 years immunized with these 2 vaccines.

RESULTS

LAIV elicited a significant increase in naive, memory, and transitional B cells on day 30 after vaccination, whereas TIV elicited an increased number of plasmablasts on day 7. Antibody titers against the 3 vaccine strains (H1N1, H3N2, and B) were significantly higher in the TIV group and correlated with number of antibody-secreting cells. Both vaccines induced overexpression of interferon (IFN)-signaling genes but with different kinetics. TIV induced expression of IFN genes on day 1 after vaccination in all age groups, and LAIV induced expression of IFN genes on day 7 after vaccination but only in children <5 years old. IFN-related genes overexpressed in both vaccinated groups correlated with H3N2 antibody titers.

CONCLUSIONS

These results suggest that LAIV and TIV induced significantly different B-cell responses in vaccinated children. Early induction of IFN appears to be important for development of antibody responses.

Epidemiology of respiratory viral infections in children enrolled in a study of influenza vaccine effectiveness

BACKGROUND

Influenza-like illness (ILI) confers a high annual morbidity in young children. We report the epidemiology of ILIs in children who participated in an influenza vaccine effectiveness study during the 2010 Southern Hemisphere influenza season in Sydney, Australia.

METHODS

Children aged 0·5-3 years were prospectively recruited from child care centres (CCCs). We classified them as fully vaccinated, partially vaccinated and unvaccinated according to their receipt of unadjuvanted vaccines containing influenza A (H1N1)pdm09. For 13 weeks commencing 30 July 2010, parents reported when their children developed an ILI (fever ≥37·8°C/feverishness plus ≥1 respiratory symptom) and collected nose and/or throat swabs for multiplex respiratory virus polymerase chain reaction (PCR) testing. Health impacts were assessed by telephone interview at enrolment and two weeks after each ILI.

RESULTS

There were 124 ILIs reported in 105 of 381 enrolled children. Swabs were taken in 117 ILIs: 175 viruses were identified from 103 swabs. Adeno- and rhinoviruses were most frequently identified; 44% of swabs yielded multiple viruses. No virus was associated with more severe symptoms, although rhinovirus-related ILIs lasted longer. Nose swabs had a higher virus detection rate than throat swabs. Influenza-vaccinated children were 1·6 times (P = 0·001) more likely than unvaccinated children to have a non-influenza ILI.

CONCLUSION

Adeno- and rhinoviruses were the most common viruses causing ILI. Swabs taken by parents are an effective method for sample collection. Influenza-like illness was more common in children vaccinated against influenza in this observational study, but prior health-seeking behaviour may have contributed to this difference.