Safety and tolerability of cold-adapted influenza virus vaccine in children and adolescents with asthma

Safety of live attenuated influenza vaccine (LAIV) in children and adults with asthma: a systematic literature review and narrative synthesis

INTRODUCTION

Asthma is one of the most common chronic respiratory conditions worldwide and can be exacerbated by influenza. Findings from early trials demonstrated a higher risk of medically significant wheezing in otherwise healthy young children (aged 6 - 23 months) following administration of the Ann Arbor-backbone live attenuated influenza vaccine (LAIV-AA). In more recent years, several additional studies have investigated the safety of LAIV-AA in older children (2 - 17 years of age) and adults with asthma or prior wheezing, but these findings have not yet been systematically evaluated.

AREAS COVERED

We conducted a systematic literature review to assess and synthesize the evidence from all available studies on the safety of LAIV-AA in people aged 2 - 49 years with a diagnosis of asthma or recurrent wheezing.

EXPERT OPINION

Fourteen studies over 20 years, involving a total of 1.2 million participants, provided evidence that LAIV-AA was well tolerated with no safety concerns in individuals aged 2 - 49 years with a diagnosis of asthma or recurrent wheezing. These data can help inform guidelines for use of LAIV-AA in children and adults with a history of asthma or recurrent wheezing.

Benefits of influenza vaccination on the associations between ambient air pollution and allergic respiratory diseases in children and adolescents: New insights from the Seven Northeastern Cities study in China

BACKGROUND

Little information exists on interaction effects between air pollution and influenza vaccination on allergic respiratory diseases. We conducted a large population-based study to evaluate the interaction effects between influenza vaccination and long-term exposure to ambient air pollution on allergic respiratory diseases in children and adolescents.

METHODS

A cross-sectional study was investigated during 2012-2013 in 94 schools from Seven Northeastern Cities (SNEC) in China. Questionnaires surveys were obtained from 56 137 children and adolescents aged 2-17 years. Influenza vaccination was defined as receipt of the influenza vaccine. We estimated air pollutants exposure [nitrogen dioxide (NO₂) and particulate matter with aerodynamic diameters ≤1 μm (PM₁), ≤2.5 μm (PM_2.5) and ≤10 μm (PM₁₀)] using machine learning methods. We employed two-level generalized linear mix effects model to examine interactive effects between influenza vaccination and air pollution exposure on allergic respiratory diseases (asthma, asthma-related symptoms and allergic rhinitis), after controlling for important covariates.

RESULTS

We found statistically significant interactions between influenza vaccination and air pollutants on allergic respiratory diseases and related symptoms (doctor-diagnosed asthma, current wheeze, wheeze, persistent phlegm and allergic rhinitis). The adjusted ORs for doctor-diagnosed asthma, current wheeze and allergic rhinitis among the unvaccinated group per interquartile range (IQR) increase in PM₁ and PM_2.5 were significantly higher than the corresponding ORs among the vaccinated group [For PM₁, doctor-diagnosed asthma: OR: 1.89 (95%CI: 1.57-2.27) vs 1.65 (95%CI: 1.36-2.00); current wheeze: OR: 1.50 (95%CI: 1.22-1.85) vs 1.10 (95%CI: 0.89-1.37); allergic rhinitis: OR: 1.38 (95%CI: 1.15-1.66) vs 1.21 (95%CI: 1.00-1.46). For PM_2.5, doctor-diagnosed asthma: OR: 1.81 (95%CI: 1.52-2.14) vs 1.57 (95%CI: 1.32-1.88); current wheeze: OR: 1.46 (95%CI: 1.21-1.76) vs 1.11 (95%CI: 0.91-1.35); allergic rhinitis: OR: 1.35 (95%CI: 1.14-1.60) vs 1.19 (95%CI: 1.00-1.42)]. The similar patterns were observed for wheeze and persistent phlegm. The corresponding p values for interactions were less than 0.05, respectively. We assessed the risks of PM₁-related and PM_2.5-related current wheeze were decreased by 26.67% (95%CI: 1.04%-45.66%) and 23.97% (95%CI: 0.21%-42.08%) respectively, which was attributable to influenza vaccination (both p for efficiency <0.05).

CONCLUSIONS

Influenza vaccination may play an important role in mitigating the detrimental effects of long-term exposure to ambient air pollution on childhood allergic respiratory diseases. Policy targeted at increasing influenza vaccination may yield co-benefits in terms of reduced allergic respiratory diseases.

Safety of guidelines recommending live attenuated influenza vaccine for routine use in children and adolescents with asthma

OBJECTIVE

Evaluate whether a guideline recommending Live Attenuated Influenza Vaccine (LAIV) for children 2 years and older with asthma increased risks for lower respiratory events (LREs), within 21 or 42 days of vaccination, as compared to standard guidelines to administer Inactivated Influenza Vaccine (IIV) in children with asthma.

METHODS

This was a pre/post guideline retrospective cohort study of children ages 2-17 years with asthma and receiving one or more influenza vaccines in two large medical groups from 2007 to 2016. Both groups recommended IIV in the pre-period; in 2010, one group implemented a guideline recommending LAIV for all children, including those with asthma. Main outcomes were medically attended LREs within 21 and 42 days after influenza immunization. Analysis used a generalized estimating equation regression to estimate the ratio of rate ratios (RORs) comparing pre/post events between LAIV guideline and control group.

RESULTS

The cohort included 7851 influenza vaccinations in 4771 children with asthma. Among patients in the LAIV guideline group, the proportion receiving LAIV increased from 23% to 68% post-guideline implementation, versus an increase from 7 to 11% in the control group. Age and baseline asthma severity adjusted ROR showed no increase in LREs, primarily asthma exacerbations, following implementation of the LAIV guideline: overall aROR (95% Confidence Interval): 0.74 (0.43-1.29) for LRE within 21 days of vaccination, 0.77 (0.53-1.14) for LRE within 42 days of vaccination. For the subset of children ages 2-4 years aROR: 0.92 (0.34-2.53) for LRE within 21 days of vaccination and 0.94 (0.49-1.82) for LRE within 42 days of vaccination; for children 5-18 years aROR (95% CI): 0.58 (0.26-1.30) for LRE within 21 days of vaccination and 0.67 (0.37-1.23) for LRE within 42 days.

CONCLUSION

In a large cohort of children with asthma, a guideline recommending LAIV rather than IIV did not increase LREs following vaccination.

Updates on Influenza Vaccination in Children

Influenza vaccination is recommended for all children 6 months of age and older who do not have contraindications. This article provides an overview of information concerning burden of influenza among children in the United States; US-licensed influenza vaccines; vaccine immunogenicity, effectiveness, and safety; and recent updates relevant to use of these vaccines in pediatric populations. Influenza antiviral medications are discussed. Details concerning vaccine-related topics may be found in the current US Centers for Disease Control and Prevention/Advisory Committee on Immunization Practices recommendations for use of influenza vaccines (https://www.cdc.gov/vaccines/hcp/acip-recs/vacc-specific/flu.html). Additional information on influenza antivirals is located at https://www.cdc.gov/flu/professionals/antivirals/index.htm.

Live attenuated influenza vaccine use and safety in children and adults with asthma

BACKGROUND

Live attenuated influenza vaccine (LAIV) might increase the risk of wheezing in persons with asthma or children younger than 5 years with a history of recurrent wheezing.

OBJECTIVE

To describe the use and assess the safety of LAIV in persons with asthma in the Vaccine Safety Datalink population.

METHODS

We identified persons with asthma using diagnosis codes and medication records in 7 health care organizations over 3 influenza seasons (2008-2009 through 2010-2011) and determined their influenza vaccination rates. Using the self-controlled risk interval method, we calculated the incidence rate ratio of medically attended respiratory events in the 14 days after LAIV compared with 29 to 42 days after vaccination in persons 2 through 49 years old.

RESULTS

In our population of 6.3 million, asthma prevalence was 5.9%. Of persons with asthma, approximately 50% received any influenza vaccine but less than 1% received LAIV. The safety study included 12,354 LAIV doses (75% in children; 93% in those with intermittent or mild persistent asthma). The incidence rate ratio for inpatient and emergency department visits for lower respiratory events (including asthma exacerbation and wheezing) was 0.98 (95% confidence interval 0.63-1.51) and the incidence rate ratio for upper respiratory events was 0.94 (95% confidence interval 0.48-1.86). The risk of lower respiratory events was similar for intermittent and mild persistent asthma, across age groups, and for seasonal trivalent LAIV and 2009 H1N1 pandemic monovalent LAIV.

CONCLUSION

LAIV use in asthma was mostly in persons with intermittent or mild persistent asthma. LAIV was not associated with an increased risk of medically attended respiratory adverse events.

The safety of influenza vaccines in children: An Institute for Vaccine Safety white paper

Most influenza vaccines are generally safe, but influenza vaccines can cause rare serious adverse events. Some adverse events, such as fever and febrile seizures, are more common in children than adults. There can be differences in the safety of vaccines in different populations due to underlying differences in genetic predisposition to the adverse event. Live attenuated vaccines have not been studied adequately in children under 2 years of age to determine the risks of adverse events; more studies are needed to address this and several other priority safety issues with all influenza vaccines in children. All vaccines intended for use in children require safety testing in the target age group, especially in young children. Safety of one influenza vaccine in children should not be extrapolated to assumed safety of all influenza vaccines in children. The low rates of adverse events from influenza vaccines should not be a deterrent to the use of influenza vaccines because of the overwhelming evidence of the burden of disease due to influenza in children.

Prevention and Control of Seasonal Influenza with Vaccines

This report updates the 2015-16 recommendations of the Advisory Committee on Immunization Practices (ACIP) regarding the use of seasonal influenza vaccines (Grohskopf LA, Sokolow LZ, Olsen SJ, Bresee JS, Broder KR, Karron RA. Prevention and control of influenza with vaccines: recommendations of the Advisory Committee on Immunization Practices, United States, 2015-16 influenza season. MMWR Morb Mortal Wkly Rep 2015;64:818-25). Routine annual influenza vaccination is recommended for all persons aged ≥6 months who do not have contraindications. For the 2016-17 influenza season, inactivated influenza vaccines (IIVs) will be available in both trivalent (IIV3) and quadrivalent (IIV4) formulations. Recombinant influenza vaccine (RIV) will be available in a trivalent formulation (RIV3). In light of concerns regarding low effectiveness against influenza A(H1N1)pdm09 in the United States during the 2013-14 and 2015-16 seasons, for the 2016-17 season, ACIP makes the interim recommendation that live attenuated influenza vaccine (LAIV4) should not be used. Vaccine virus strains included in the 2016-17 U.S. trivalent influenza vaccines will be an A/California/7/2009 (H1N1)-like virus, an A/Hong Kong/4801/2014 (H3N2)-like virus, and a B/Brisbane/60/2008-like virus (Victoria lineage). Quadrivalent vaccines will include an additional influenza B virus strain, a B/Phuket/3073/2013-like virus (Yamagata lineage).Recommendations for use of different vaccine types and specific populations are discussed. A licensed, age-appropriate vaccine should be used. No preferential recommendation is made for one influenza vaccine product over another for persons for whom more than one licensed, recommended product is otherwise appropriate. This information is intended for vaccination providers, immunization program personnel, and public health personnel. Information in this report reflects discussions during public meetings of ACIP held on October 21, 2015; February 24, 2016; and June 22, 2016. These recommendations apply to all licensed influenza vaccines used within Food and Drug Administration-licensed indications, including those licensed after the publication date of this report. Updates and other information are available at CDC's influenza website (http://www.cdc.gov/flu). Vaccination and health care providers should check CDC's influenza website periodically for additional information.

Post-licensure surveillance of quadrivalent live attenuated influenza vaccine United States, Vaccine Adverse Event Reporting System (VAERS), July 2013-June 2014

BACKGROUND

Quadrivalent live attenuated influenza vaccine (LAIV4) was approved in 2012 for healthy persons aged 2-49 years. Beginning with the 2013-2014 influenza season, LAIV4 replaced trivalent live attenuated influenza vaccine (LAIV3).

METHODS

We analyzed LAIV4 reports to VAERS, a national spontaneous reporting system. LAIV4 reports in 2013-2014 were compared to LAIV3 reports from the previous three influenza seasons. Medical records were reviewed for non-manufacturer serious reports (i.e., death, hospitalization, prolonged hospitalization, life-threatening illness, permanent disability) and reports of selected conditions of interest. We conducted Empirical Bayesian data mining to identify disproportional reporting for LAIV4.

RESULTS

In 2013-2014, 12.7 million doses of LAIV4 were distributed and VAERS received 779 reports in individuals aged 2-49 years; 95% were non-serious. Expired drug administered (42%), fever (13%) and cough (8%) were most commonly reported in children aged 2-17 years when LAIV4 was administered alone, while headache (18%), expired drug administered (15%) and exposure during pregnancy (12%) were most common in adults aged 18-49 years. We identified one death report in a child who died from complications of cerebellar vascular tumors. Among non-death serious reports, neurologic conditions were common in children and adults. In children, seizures (3) and Guillain-Barré syndrome (2) were the most common serious neurologic outcomes. We identified three serious reports of asthma/wheezing following LAIV4 in children. Data mining detected disproportional reporting for vaccine administration errors and for influenza illness in children.

CONCLUSIONS

Our analysis of VAERS reports for LAIV4 did not identify any concerning patterns. The data mining finding for reports of influenza illness is consistent with low LAIV4 vaccine effectiveness observed for influenza A disease in children in 2013-2014. Reports of LAIV4 administration to persons in whom the vaccine is not recommended (e.g., pregnant women) indicate the need for education, training and screening regarding indications.

Vaccinating high-risk children with the intranasal live-attenuated influenza vaccine: the Quebec experience

Given the burden of illness associated with influenza, vaccination is recommended for individuals at high risk of complications. The live-attenuated influenza vaccine (LAIV) is administered by intranasal spray, thus directly stimulating mucosal immunity. In this review, we aimed to provide evidence for its efficacy and safety in different paediatric populations. We also share the Quebec experience of LAIV use through a publicly funded vaccination program for children with chronic, high-risk conditions.

RESULTS

from randomized controlled trials in healthy children and in asthmatics have demonstrated superior efficacy of LAIV over the injectable vaccine (IIV). LAIV is well tolerated: its administration is associated with runny nose and nasal congestion, but not with asthma exacerbations and is well tolerated in children with cystic fibrosis, when compared to IIV. The vaccine is well accepted by children and parents and can easily be part of vaccination clinics in paediatric tertiary care centres targeting children with chronic, high-risk conditions, not leading to immunosuppression.

Vaccination of children with a live-attenuated, intranasal influenza vaccine - analysis and evaluation through a Health Technology Assessment

BACKGROUND

Influenza is a worldwide prevalent infectious disease of the respiratory tract annually causing high morbidity and mortality in Germany. Influenza is preventable by vaccination and this vaccination is so far recommended by the The German Standing Committee on Vaccination (STIKO) as a standard vaccination for people from the age of 60 onwards. Up to date a parenterally administered trivalent inactivated vaccine (TIV) has been in use almost exclusively. Since 2011 however a live-attenuated vaccine (LAIV) has been approved additionally. Consecutively, since 2013 the STIKO recommends LAIV (besides TIV) for children from 2 to 17 years of age, within the scope of vaccination by specified indications. LAIV should be preferred administered in children from 2 to 6 of age. The objective of this Health Technology Assessment (HTA) is to address various research issues regarding the vaccination of children with LAIV. The analysis was performed from a medical, epidemiological and health economic perspective, as well as from an ethical, social and legal point of view.

METHOD

An extensive systematic database research was performed to obtain relevant information. In addition a supplementary research by hand was done. Identified literature was screened in two passes by two independent reviewers using predefined inclusion and exclusion criteria. Included literature was evaluated in full-text using acknowledged standards. Studies were graded with the highest level of evidence (1++), if they met the criteria of European Medicines Agency (EMA)-Guidance: Points to consider on applications with 1. meta-analyses; 2. one pivotal study.

RESULTS

For the medical section, the age of the study participants ranges from 6 months to 17 years. Regarding study efficacy, in children aged 6 months to ≤7 years, LAIV is superior to placebo as well as to a vac-cination with TIV (Relative Risk Reduction - RRR - of laboratory confirmed influenza infection approx. 80% and 50%, respectively). In children aged >7 to 17 years (= 18th year of their lives), LAIV is superior to a vaccination with TIV (RRR 32%). For this age group, no studies that compared LAIV with placebo were identified. It can be concluded that there is high evidence for superior efficacy of LAIV (compared to placebo or TIV) among children aged 6 months to ≤7 years. For children from >7 to 17 years, there is moderate evidence for superiority of LAIV for children with asthma, while direct evidence for children from the general population is lacking for this age group. Due to the efficacy of LAIV in children aged 6 months to ≤7 years (high evidence) and the efficacy of LAIV in children with asthma aged >7 to 17 years (moderate evidence), LAIV is also very likely to be efficacious among children in the general population aged >7 to 17 years (indirect evidence). In the included studies with children aged 2 to 17 years, LAIV was safe and well-tolerated; while in younger children LAIV may increase the risk of obstruction of the airways (e.g. wheezing). In the majority of the evaluated epidemiological studies, LAIV proved to be effective in the prevention of influenza among children aged 2-17 years under everyday conditions (effectiveness). The trend appears to indicate that LAIV is more effective than TIV, although this can only be based on limited evidence for methodological reasons (observational studies). In addition to a direct protective effect for vaccinated children themselves, indirect protective ("herd protection") effects were reported among non-vaccinated elderly population groups, even at relatively low vaccination coverage of children. With regard to safety, LAIV generally can be considered equivalent to TIV. This also applies to the use among children with mild chronically obstructive conditions, from whom LAIV therefore does not have to be withheld. In all included epidemiological studies, there was some risk of bias identified, e.g. due to residual confounding or other methodology-related sources of error. In the evaluated studies, both the vaccination of children with previous illnesses and the routine vaccination of (healthy) children frequently involve cost savings. This is especially the case if one includes indirect costs from a societal perspective. From a payer perspective, a routine vaccination of children is often regarded as a highly cost-effective intervention. However, not all of the studies arrive at consistent results. In isolated cases, relatively high levels of cost-effectiveness are reported that make it difficult to perform a conclusive assessment from an economic perspective. Based on the included studies, it is not possible to make a clear statement about the budget impact of using LAIV. None of the evaluated studies provides results for the context of the German healthcare setting. The efficacy of the vaccine, physicians' recommendations, and a potential reduction in influenza symptoms appear to play a role in the vaccination decision taken by parents/custodians on behalf of their children. Major barriers to the utilization of influenza vaccination services are a low level of perception and an underestimation of the disease risk, reservations concerning the safety and efficacy of the vaccine, and potential side effects of the vaccine. For some of the parents surveyed, the question as to whether the vaccine is administered as an injection or nasal spray might also be important.

CONCLUSION

In children aged 2 to 17 years, the use of LAIV can lead to a reduction of the number of influenza cases and the associated burden of disease. In addition, indirect preventive effects may be expected, especially among elderly age groups. Currently there are no data available for the German healthcare setting. Long-term direct and indirect effectiveness and safety should be supported by surveillance programs with a broader use of LAIV. Since there is no general model available for the German healthcare setting, statements concerning the cost-effectiveness can be made only with precaution. Beside this there is a need to conduct health eco-nomic studies to show the impact of influenza vaccination for children in Germany. Such studies should be based on a dynamic transmission model. Only these models are able to include the indirect protective effects of vaccination correctly. With regard to ethical, social and legal aspects, physicians should discuss with parents the motivations for vaccinating their children and upcoming barriers in order to achieve broader vaccination coverage. The present HTA provides an extensive basis for further scientific approaches and pending decisions relating to health policy.

Effectiveness and safety of seasonal influenza vaccination in children with underlying respiratory diseases and allergy

Influenza causes acute respiratory infections and various complications. Children in the high-risk group have higher complication and hospitalization rates than high-risk elderly individuals. Influenza prevention in children is important, as they can be a source infection spread in their communities. Influenza vaccination is strongly recommended for high-risk children with chronic underlying circulatory and respiratory disease, immature infants, and children receiving long-term immunosuppressant treatment or aspirin. However, vaccination rates in these children are low because of concerns regarding the exacerbation of underlying diseases and vaccine efficacy. To address these concerns, many clinical studies on children with underlying respiratory diseases have been conducted since the 1970s. Most of these reported no differences in immunogenicity or adverse reactions between healthy children and those with underlying respiratory diseases and no adverse effects of the influenza vaccine on the disease course. Further to these studies, the inactivated split-virus influenza vaccine is recommended for children with underlying respiratory disease, in many countries. However, the live-attenuated influenza vaccine (LAIV) is not recommended for children younger than 5 years with asthma or recurrent wheezing. Influenza vaccination is contraindicated in patients with severe allergies to egg, chicken, or feathers, because egg-cultivated influenza vaccines may contain ovalbumin. There has been no recent report of serious adverse events after influenza vaccination in children with egg allergy. However, many experts recommend the trivalent influenza vaccine for patients with severe egg allergy, with close observation for 30 minutes after vaccination. LAIV is still not recommended for patients with asthma or egg allergy.

Vaccines for preventing influenza in people with asthma

BACKGROUND

Influenza vaccination is recommended for asthmatic patients in many countries as observational studies have shown that influenza infection can be associated with asthma exacerbations. However, influenza vaccination has the potential to cause wheezing and adversely affect pulmonary function. While an overview concluded that there was no clear benefit of influenza vaccination in patients with asthma, this conclusion was not based on a systematic search of the literature.

OBJECTIVES

The objective of this review was to assess the efficacy and safety of influenza vaccination in children and adults with asthma.

SEARCH METHODS

We searched the Cochrane Airways Group trials register and reviewed reference lists of articles. The latest search was carried out in November 2012.

SELECTION CRITERIA

We included randomised trials of influenza vaccination in children (over two years of age) and adults with asthma. We excluded studies involving people with chronic obstructive pulmonary disease.

DATA COLLECTION AND ANALYSIS

Inclusion criteria and assessment of trial quality were applied by two review authors independently. Data extraction was done by two review authors independently. Study authors were contacted for missing information.

MAIN RESULTS

Nine trials were included in the first published version of this review, and nine further trials have been included in four updates. The included studies cover a wide diversity of people, settings and types of influenza vaccination, and we pooled data from the studies that employed similar vaccines. PROTECTIVE EFFECTS OF INACTIVATED INFLUENZA VACCINE DURING THE INFLUENZA SEASON: A single parallel-group trial, involving 696 children, was able to assess the protective effects of influenza vaccination. There was no significant reduction in the number, duration or severity of influenza-related asthma exacerbations. There was no difference in the forced expiratory volume in one second (FEV) although children who had been vaccinated had better symptom scores during influenza-positive weeks. Two parallel-group trials in adults did not contribute data to these outcomes due to very low levels of confirmed influenza infection. ADVERSE EFFECTS OF INACTIVATED INFLUENZA VACCINE IN THE FIRST TWO WEEKS FOLLOWING VACCINATION: Two cross-over trials involving 1526 adults and 712 children (over three years old) with asthma compared inactivated trivalent split-virus influenza vaccine with a placebo injection. These trials excluded any clinically important increase in asthma exacerbations in the two weeks following influenza vaccination (risk difference 0.014; 95% confidence interval -0.010 to 0.037). However, there was significant heterogeneity between the findings of two trials involving 1104 adults in terms of asthma exacerbations in the first three days after vaccination with split-virus or surface-antigen inactivated vaccines. There was no significant difference in measures of healthcare utilisation, days off school/symptom-free days, mean lung function or medication usage.EFFECTS OF LIVE ATTENUATED (INTRANASAL) INFLUENZA VACCINATION: There were no significant differences found in exacerbations or measures of lung function following live attenuated cold recombinant vaccine versus placebo in two small studies on 17 adults and 48 children. There were no significant differences in asthma exacerbations found for the comparison live attenuated vaccine (intranasal) versus trivalent inactivated vaccine (intramuscular) in one study on 2229 children (over six years of age).

AUTHORS' CONCLUSIONS

Uncertainty remains about the degree of protection that vaccination affords against asthma exacerbations that are related to influenza infection. Evidence from more recently published randomised trials of inactivated split-virus influenza vaccination indicates that there is no significant increase in asthma exacerbations immediately after vaccination in adults or children over three years of age. We were unable to address concerns regarding possible increased wheezing and hospital admissions in infants given live intranasal vaccination.

Assessing the safety of influenza vaccination in specific populations: children and the elderly

Comprehensive monitoring of the safety of influenza vaccines remains a public health priority, particularly as immunization coverage increases across different age groups at the global level. In this review, the authors provide state-of-the-art knowledge on the safety of influenza immunization among children and the elderly. The authors review the safety information in each group separately for inactivated and live attenuated influenza vaccines. Adverse events of special concern including febrile seizure, narcolepsy, asthma and Guillain-Barré syndrome are covered under specific considerations. The authors discuss the current status of the field, particularly the use of new technologies for influenza vaccines and their potential safety profile.

Efficacy and safety of influenza vaccination in children with asthma

The mean global prevalence of asthma among children is approximately 12%, making it the most common chronic disease in children. Influenza infection has been associated with complications such as exacerbations of wheezing and asthma, increased airway hyper-reactivity and hospitalization. Although influenza vaccination is recommended for asthmatic patients by all health authorities, vaccination coverage remains significantly lower than expected and is lowest of all in children. Compliance is affected by the uncertainty of parents and physicians concerning the clinical risk of influenza in asthmatic subjects, the benefits of influenza vaccination in preventing asthma exacerbations and the safety of immunization. The aim of this review is to analyze the rationale for using influenza vaccine, discuss the relationship between influenza and the severity of asthmatic episodes and document the efficacy and safety of influenza vaccination in the pediatric asthmatic population.

The safety and efficacy of live attenuated influenza vaccine in young children with asthma or prior wheezing

In the European Union and Canada, an Ann Arbor strain live attenuated influenza vaccine (LAIV) is approved for use in children aged 2–17 years, including those with mild to moderate asthma or prior wheezing. The safety and efficacy of LAIV versus trivalent inactivated influenza vaccine (TIV) in children with asthma aged 6–17 years have been demonstrated. However, few data are available for children younger than 6 years of age with asthma or prior wheezing. Safety and efficacy data were collected for children aged 2–5 years with asthma or prior wheezing from two randomized, multinational trials of LAIV and TIV (N = 1,940). Wheezing, lower respiratory illness, and hospitalization were not significantly increased among children receiving LAIV compared with TIV. Increased upper respiratory symptoms and irritability were observed among LAIV recipients (p < 0.05). Relative efficacies were consistent with the results observed in the overall study populations, which demonstrated fewer cases of culture-confirmed influenza illness in LAIV compared with TIV recipients. Study results support the safety and efficacy of LAIV among children aged 2–17 years with mild to moderate asthma or a history of wheezing. Data regarding LAIV use are limited among individuals with severe asthma or active wheezing within the 7 days before vaccination.

Live attenuated intranasal influenza vaccine

Annual vaccination is the most effective means of preventing and controlling influenza epidemics, and the traditional trivalent inactivated vaccine (TIV) is by far the most widely used. Unfortunately, it has a number of limitations, the most important of which is its poor immunogenicity in younger children and the elderly, the populations at greatest risk of severe influenza. Live attenuated influenza vaccine (LAIV) has characteristics that can overcome some of these limitations. It does not have to be injected because it is administered intranasally. It is very effective in children and adolescents, among whom it prevents significantly more cases of influenza than the traditional TIV. However, its efficacy in adults has not been adequately documented, which is why it has not been licensed for use by adults by the European health authorities. LAIV is safe and well tolerated by children aged > 2 y and adults, but some concerns arisen regarding its safety in younger children and subjects with previous asthma or with recurrent wheezing. Further studies are needed to solve these problems and to evaluate the possible role of LAIV in the annual vaccination of the general population.

Influenza vaccination, diagnosis, and treatment in children

Between 2009 and 2010, the influenza H1N1 pandemic swept across the globe, disproportionately affecting the pediatric population. This pandemic strain is expected to circulate again with other seasonal influenza strains during the 2010-2011 season. This article reviews the new 2010 to 2011 Centers for Disease Control and Prevention and American Academy of Pediatrics recommendations for vaccination against the influenza virus for pediatric patients. It reviews the various testing modalities and the benefits and disadvantage of each test and offers an approach to diagnostic testing. Lastly, it reviews the indications and recommendations for treatment of children with presumed or confirmed influenza infection.

Asthma prevalence and exacerbations in children: is there an association with childhood vaccination?

Infections and vaccinations may have a potential role in the normal maturation of the immune system, in the development and balance of regulatory pathways, and in the development and exacerbations of asthma. Asthma exacerbations often result from respiratory viral infections, and, while vaccination towards common viral infections may reduce the occurrence of such exacerbations, there has been concern that vaccinations can increase the risk of asthma. Current studies show that childhood vaccines, including inactivated influenza vaccine, are generally safe. However, there is some concern regarding possible exacerbations in infants or children with frequent wheezing or persistent asthma who are given live-attenuated influenza vaccination. Although severe allergic adverse events attributable to vaccination are extremely rare, all serious allergic reactions should be further assessed to detect the likely causative vaccine component, such as egg protein or gelatin. The risks of not vaccinating children far outweigh the risks of allergy and asthma exacerbations. Therefore, childhood vaccination should remain an essential part of child health programs and should not be withheld, even from children with asthma or those predisposed to allergy.

Update on vaccination guidelines for allergic children

Children with allergic or atopic diseases require immunization just like non-atopic children. However, vaccination of such children requires some special considerations and precautions. Children may be allergic to specific vaccine constituents such as gelatin or egg. Children who have suffered an apparent allergic reaction to a vaccine should be evaluated by an allergist to determine the culprit allergen and to make recommendations regarding future vaccination. In rare circumstances, certain vaccines may cause acute exacerbations of allergic diseases, but the contention that vaccination causes allergic disease is not substantiated by any available evidence.

Immunization with live influenza viruses in an experimental model of allergic bronchial asthma: infection and vaccination

BACKGROUND

Asthmatics in particular have a need for influenza vaccines because influenza infection is a frequent cause of hospitalization of patients with bronchial asthma. Currently, only inactivated influenza vaccines are recommended for influenza prevention in asthma sufferers.

OBJECTIVE

The aim of our study was to analyze and compare the effects of influenza infection and vaccination with live attenuated influenza vaccine (LAIV) on different phases of experimental murine allergic bronchial asthma (acute asthma and remission phase) and on subsequent exposure to allergen in sensitized animals.

METHODS

Ovalbumin (OVA)-specific serum IgE levels, IL-4 production by spleen and lung lymphocytes, and histological changes in the lungs of mice infected with pathogenic virus or LAIV were studied at two phases of OVA-induced bronchial asthma (acute asthma and remission). Results Infection with pathogenic virus both in acute asthma and remission led to asthma exacerbation associated with the production of OVA-specific IgE, IL-4 and significant inflammatory infiltration in airways. Infection, even after complete virus clearance, induced the aggravation of lung inflammation and IgE production in asthmatic mice additionally exposed to OVA. Immunization with LAIV at remission did not enhance allergic inflammatory changes in the lung, OVA-specific IgE or IL-4 production. Then after additional OVA exposure, histological and immunological changes in these mice were the same as in the control group.

CONCLUSIONS

Influenza infection provokes asthma exacerbation regardless of the disease phase. Immunization with LAIV during the remission phase of bronchial asthma is safe and does not interfere upon subsequent contact of asthma sufferers with allergen.

The Role of Influenza Vaccination in Asthmatic Children

Asthma is the most occurring chronic disease in children. Asthma related genes and environmental factors play a role in the etiology. Nowadays, asthma is regarded as a chronic inflammatory disease of the airways instead of solely a reversible airway obstruction. Asthma is often diagnosed on specific symptoms such as chest tightness, wheezing, dyspnea, and coughing. It is likely that, rather than a single disease entity, asthma consists of related, partially overlapping syndromes. The first symptoms often are experienced before the age of 5. Children with the highest risk have a family history of atopy and/or asthma. Viral infections with symptoms of wheezing acquired in the first year of life may be associated with the risk of developing asthma later on [1]. However, making the diagnosis with a reasonable certainty that is supported by spirometry is only possible from the age of 6 onward. More than 50% of children with a period of wheezing earlier on in life are not diagnosed as having asthma at the age of 6 [2].

The use of rescue and anti-inflammatory medication has largely altered the prospects of asthma patients and has improved their quality of life. Thus, nowadays, most asthma patients lead a normal life without restrictions. Disease control achieved by the asthmatics is an important predictor of the likelihood of complications of the disease [3]. However, asthma exacerbations neither respond to inhaled steroids nor can they substantially be prevented in this way [4, 5]. Only the use of oral corticos-teroids seems to be unmistakably effective in case of exacerbations [6, 7].

Safety of the intranasal, trivalent, live attenuated influenza vaccine (LAIV) in children with intermittent wheezing in an open-label field trial

BACKGROUND

Safety of the intranasal, trivalent, live attenuated influenza vaccine (LAIV) in children with asthma is unknown. A previous report showed an "asthma signal" in children aged 18-35 months.

METHODS

Healthy children aged 1.5-18 years with history of intermittent wheezing received single annual LAIV doses during a 4-year trial. Rates of medically-attended acute respiratory illnesses, including acute asthma exacerbation, during 0-14 and 0-42 days post-LAIV were compared with respective reference periods (before day 0 and after 14 or 42 days). To assess the risk of new-onset asthma, LAIV recipients without history of wheezing were analyzed.

RESULTS

During each of the 4 years, 454, 656, 656, and 430 children, respectively, with intermittent wheezing who received LAIV had no increased risk for medically-attended acute respiratory illnesses, including asthma exacerbation. First-dose LAIV recipients, including those aged 1.5-4 years, and those receiving 2-4 consecutive annual doses had no increased risk. Children with parents' report of intermittent wheezing and those with administrative database codes for asthma during 2 prior years had no increased risk. During the 4 years, 2952, 3092, 2953, and 2478 children without history of wheezing had no increased risk of new-onset asthma.

CONCLUSIONS

LAIV administration in children aged 1.5-18 years with history of intermittent wheezing was safe, and was not associated with increased risk for medically-attended acute respiratory illnesses, including acute asthma exacerbation. This was true for the first and 2-4 consecutive annual doses. Parents' report of intermittent wheezing was reliable. First-dose LAIV was not associated with new-onset asthma in children without history of wheezing.

Vaccines for preventing influenza in people with asthma

BACKGROUND

Influenza vaccination is recommended for asthmatic patients in many countries as observational studies have shown that influenza infection can be associated with asthma exacerbations, but influenza vaccination itself has the potential to adversely affect pulmonary function. A recent overview concluded that there was no clear benefit of influenza vaccination in patients with asthma but this conclusion was not based on a systematic search of the literature.

OBJECTIVES

Whilst influenza may cause asthma exacerbations, there is controversy about the use of influenza vaccinations, since they may precipitate an asthma attack in some people. The objective of this review was to assess the efficacy of influenza vaccination in children and adults with asthma.

SEARCH STRATEGY

We searched the Cochrane Airways Group trials register and checked reference lists of articles. The last search was carried out in September 2007.

SELECTION CRITERIA

Randomised trials of influenza vaccination in children (over two years of age) and adults with asthma. Studies involving people with chronic obstructive pulmonary disease were excluded.

DATA COLLECTION AND ANALYSIS

Inclusion criteria and assessment of trial quality were applied by two reviewers independently. Data extraction was done by two reviewers independently. Study authors were contacted for missing information.

MAIN RESULTS

Nine trials were initially included. Four of these trials were of high quality. Six further articles have been included in three updates (Bueving 2003; Castro 2001; Fleming 2006; Redding 2002; Reid 1998). The included studies covered a wide diversity of people, settings and types of influenza vaccination, but data from the more recent studies that used similar vaccines have been pooled.

BENEFITS

Bueving 2003 studied 696 children with asthma and did not demonstrate a significant reduction in influenza related asthma exacerbations (Risk Difference 0.01; 95% confidence interval -0.02 to 0.04).

HARMS

The pooled results of two trials involving 2306 people with asthma did not demonstrate a significant increase in asthma exacerbations in the two weeks following influenza vaccination (Risk Difference 0.00; 95% confidence interval -0.02 to 0.02).

AUTHORS' CONCLUSIONS

Uncertainty remains about the degree of protection vaccination affords against asthma exacerbations that are related to influenza infection. Evidence from recently published trials indicates that there is no significant increase in asthma exacerbations immediately after vaccination (at least with inactivated influenza vaccination). There is concern regarding possible increased wheezing and hospital admissions in infants given live intranasal vaccination.

Flu myths: dispelling the myths associated with live attenuated influenza vaccine

Live attenuated influenza vaccine (LAIV), commercially available since 2003, has not gained widespread acceptance among prescribers. This underuse can be traced to several misperceptions and fears regarding LAIV. This review examines both the facts (safety, immunogenicity, and effectiveness) and the most pervasive myths about LAIV. Live attenuated influenza vaccine is a safe, highly immunogenic, and effective vaccine. It is well tolerated; only mild and transient upper respiratory infection symptoms occur with LAIV vs placebo, even in higher-risk patients with asthma or the early stages of human immunodeficiency virus. It is immunogenic, especially in induction of mucosal immunity. In certain populations, LAIV is as effective as, and in some cases more effective than, inactivated influenza in preventing influenza infection. It appears to be more effective in preventing influenza infection than trivalent inactivated influenza vaccine when the vaccine virus strain does not closely match that of the circulating wild-type virus. Many myths and misperceptions about the vaccine exist, foremost among them the myth of genetic reversion. Independent mutation in 4 gene segments would be required for reversion of the vaccine strain of influenza virus to a wild type, an unlikely and as yet unobserved event. Although shedding of vaccine virus is common, transmission of vaccine virus has been documented only in a single person, who remained asymptomatic. In the age groups for which it is indicated, LAIV is a safe and effective vaccine to prevent influenza infection.

Comparative immunogenicities of frozen and refrigerated formulations of live attenuated influenza vaccine in healthy subjects

The frozen version of live attenuated influenza vaccine (LAIV; FluMist) was compared with a newly licensed, refrigerated formulation, the cold-adapted influenza vaccine, trivalent (CAIV-T), for their immunogenicity, safety, and tolerability in healthy subjects 5 to 49 years of age. Eligible subjects were randomized 1:1 to receive CAIV-T or frozen LAIV. Subjects 5 to 8 years of age received two doses of vaccine 46 to 60 days apart; subjects 9 to 49 years of age received one dose of vaccine. Equivalent immunogenicities were defined as serum hemagglutination inhibition (HAI) geometric mean titer (GMT) ratios >0.5 and <2.0 for each of the three vaccine-specific strains. A total of 376 subjects 5 to 8 years of age and 566 subjects 9 to 49 years of age were evaluable. Postvaccination HAI GMT ratios were equivalent for CAIV-T and LAIV. The GMT ratios of CAIV-T/LAIV for the H1N1, H3N2, and B strains were 1.24, 1.02, and 1.00, respectively, for the 5- to 8-year-old age group and 1.14, 1.12, and 0.96, respectively, for the 9- to 49-year-old age group. Seroresponse/seroconversion rates (fourfold or greater rise) were similar in both age groups for each of the three vaccine strains. Within 28 days, the most frequent reactogenicity event in the CAIV-T and LAIV groups was runny nose/nasal congestion, which occurred at higher rates after dose 1 (44% and 42%, respectively) than after dose 2 (41% and 29%, respectively) in the 5- to 8-year-old group. Otherwise, the rates of adverse events (AEs) were similar between the treatment groups and the two age cohorts, with no serious AEs related to the study vaccines. The immunogenicities, reactogenicity events, and AEs were comparable for refrigerated CAIV-T and frozen LAIV.

Superior relative efficacy of live attenuated influenza vaccine compared with inactivated influenza vaccine in young children with recurrent respiratory tract infections

BACKGROUND

Young children have a high incidence of influenza and influenza-related complications. This study compared the efficacy and safety of cold-adapted influenza vaccine, trivalent (CAIV-T) with trivalent inactivated influenza vaccine (TIV) in young children with a history of recurrent respiratory tract infections (RTIs).

METHODS

Children 6 to 71 months of age were randomized to receive 2 doses of CAIV-T (n = 1101) or TIV (n = 1086), 35 +/- 7 days apart before the start of the 2002-2003 influenza season and were followed up for culture-confirmed influenza, effectiveness outcomes, reactogenicity, and adverse events.

RESULTS

Overall, 52.7% (95% confidence interval [CI] = 21.6%-72.2%) fewer cases of influenza caused by virus strains antigenically similar to vaccine were observed in CAIV-T than in TIV recipients. Greater relative efficacy for CAIV-T was observed for the antigenically similar A/H1N1 (100.0%; 95% CI = 42.3%-100.0%) and B (68.0%; 95% CI = 37.3%-84.8%) strains but not for the antigenically similar A/H3N2 strains (-97.1%; 95% CI = -540.2% to 31.5%). Relative to TIV, CAIV-T reduced the number of RTI-related healthcare provider visits by 8.9% (90% CI = 1.5%-15.8%) and missed days of school, kindergarten, or day care by 16.2% (90% CI = 10.4%-21.6%). Rhinitis and rhinorrhea, otitis media, and decreased appetite were the only events that were reported more frequently in CAIV-T subjects. There was no difference between groups in the incidence of wheezing after vaccination.

CONCLUSIONS

CAIV-T was well tolerated in these children with RTIs and demonstrated superior relative efficacy compared with TIV in preventing influenza illness.

Comparison of the efficacy and safety of live attenuated cold-adapted influenza vaccine, trivalent, with trivalent inactivated influenza virus vaccine in children and adolescents with asthma

BACKGROUND

Despite their potential for increased morbidity, 75% to 90% of asthmatic children do not receive influenza vaccination. Live attenuated influenza vaccine (LAIV), a cold-adapted, temperature-sensitive, trivalent influenza vaccine, is approved for prevention of influenza in healthy children 5 to 19 years of age. LAIV has been studied in only a small number of children with asthma.

METHODS

Children 6 to 17 years of age, with a clinical diagnosis of asthma, received a single dose of either intranasal CAIV-T (an investigational refrigerator-stable formulation of LAIV; n = 1114) or injectable trivalent inactivated influenza vaccine (TIV; n = 1115) in this randomized, open-label study during the 2002-2003 influenza season. Participants were followed up for culture-confirmed influenza illness, respiratory outcome, and safety.

RESULTS

The incidence of community-acquired culture-confirmed influenza illness was 4.1% (CAIV-T) versus 6.2% (TIV), demonstrating a significantly greater relative efficacy of CAIV-T versus TIV of 34.7% (90% confidence interval [CI] 9.4%-53.2%; 95% CI = 3.9%-56.0%). There were no significant differences between treatment groups in the incidence of asthma exacerbations, mean peak expiratory flow rate findings, asthma symptom scores, or nighttime awakening scores. The incidence of runny nose/nasal congestion was higher for CAIV-T (66.2%) than TIV (52.5%) recipients. Approximately 70% of TIV recipients reported injection site reactions.

CONCLUSIONS

CAIV-T was well tolerated in children and adolescents with asthma. There was no evidence of a significant increase in adverse pulmonary outcomes for CAIV-T compared with TIV. CAIV-T had a significantly greater relative efficacy of 35% compared with TIV in this high-risk population.

Influenza vaccine in patients with asthma

Influenza virus continues to be a major cause of respiratory infection and is an important contributor to morbidity and mortality in at-risk populations, including those with underlying pulmonary conditions such as asthma. Vaccination with inactivated influenza vaccine remains the most popular method in controlling influenza through prevention. Current guidelines recommend the administration of the influenza vaccine to all patients with asthma. However, a third or fewer of those patients with asthma are currently receiving this vaccine. In this review, the risk-versus-benefit of influenza vaccination in children and adults with asthma is evaluated, based on the current evidence.

Live attenuated influenza vaccine, trivalent, is safe in healthy children 18 months to 4 years, 5 to 9 years, and 10 to 18 years of age in a community-based, nonrandomized, open-label trial

OBJECTIVE

Influenza-associated deaths in healthy children that were reported during the 2003-2004 influenza season heightened the public awareness of the seriousness of influenza in children. In 1996-1998, a pivotal phase III trial was conducted in children who were 15 to 71 months of age. Live attenuated influenza vaccine, trivalent (LAIV-T), was shown to be safe and efficacious. In a subsequent randomized, double-blind, placebo-controlled LAIV-T trial in children who were 1 to 17 years of age, a statistically significant increase in asthma encounters was observed for children who were younger than 59 months. LAIV-T was not licensed to children who were younger than 5 years because of the concern for asthma. We report on the largest safety study to date of the recently licensed LAIV-T in children 18 months to 4 years, 5 to 9 years, and 10 to 18 years of age in a 4-year (1998-2002) community-based trial that was conducted at Scott & White Memorial Hospital and Clinic (Temple, TX).

METHODS

An open-label, nonrandomized, community-based trial of LAIV-T was conducted before its licensure. Medical records of all children were surveyed for serious adverse events (SAEs) 6 weeks after vaccination. Health care utilization was evaluated by determining the relative risk (RR) of medically attended acute respiratory illness (MAARI) and asthma rates at 0 to 14 and 15 to 42 days after vaccination compared with the rates before vaccination. Medical charts of all visits coded as asthma were reviewed for appropriate classification of events: acute asthma or other. We evaluated the risk for MAARI (health care utilization for acute respiratory illness) 0 to 14 and 15 to 42 days after LAIV-T by a method similar to the postlicensure safety analysis conducted on measles, mumps, and rubella and on diphtheria, tetanus, and whole-cell pertussis vaccines.

RESULTS

All children regardless of age were administered a single intranasal dose of LAIV-T in each vaccine year. In the 4 years of the study, we administered 18780 doses of LAIV-T to 11096 children. A total of 4529, 7036, and 7215 doses of LAIV-T were administered to children who were 18 months to 4 years, 5 to 9 years, and 10 to 18 years of age, respectively. In vaccination years 1, 2, 3, and 4, we identified 10, 15, 11, and 6 SAEs, respectively. None of the SAEs was attributed to LAIV-T. In vaccination years 1, 2, 3, and 4, we identified 3, 2, 1, and 0 pregnancies, respectively, among adolescents. All delivered healthy infants. The RR for MAARI from 0 to 14 and 15 to 42 days after LAIV-T was assessed in vaccinees during the 4 vaccine years. Compared with the prevaccination period, there was no significant increase in risk in health care utilization attributed to MAARI from 0 to 14 and 15 to 42 days after vaccination in children who were 18 months to 4 years, 5 to 9 years, and 10 to 18 years of age in the 4 vaccine years. In children who were 18 months to 4 years of age, there was no significant increase in the risk in health care utilization for MAARI, MAARI subcategories (otitis media/sinusitis, upper respiratory tract illness, and lower respiratory tract illness), and asthma during the 0 to 14 days after vaccination compared with the prevaccination period. No significant increase in the risk in health care utilization for MAARI, MAARI subcategories, and asthma was detected when the risk period was extended to 15 to 42 days after vaccination, except for asthma events in vaccine year 1. A RR of 2.85 (95% confidence interval [CI]: 1.01-8.03) for asthma events was detected in children who were 18 months to 4 years of age but was not significantly increased for the other 3 vaccine years (vaccine year 2, RR: 1.42 [95% CI: 0.59-3.42]; vaccine year 3, RR: 0.47 [95% CI: 0.12-1.83]; vaccine year 4, RR: 0.20 [95% CI: 0.03-1.54]). No significant increase in the risk in health care utilization for MAARI or asthma was observed in children who were 18 months to 18 years of age and received 1, 2, 3, or 4 annual sequential doses of LAIV-T. Children who were 18 months to 4 years of age and received 1, 2, 3, or 4 annual doses of LAIV-T did not experience a significant increase in the RR for MAARI 0 to 14 days after vaccination; this was also true for children who were 5 to 9 and 10 to 18 years of age.

CONCLUSIONS

We observed no increased risk for asthma events 0 to 14 days after vaccination in children who were 18 months to 4 years, 5 to 9 years, and 10 to 18 years of age, In vaccine year 1, children who were 18 months to 4 years of age did have a significantly higher RR (2.85; 95% CI: 1.01-8.03) for asthma events 15 to 42 days after vaccination. In vaccine year 2, the formulation of LAIV-T was identical to the vaccine formulation used in vaccine year 1; however, in children who were 18 months to 4 years of age, no statistically significant increased risk was detected for asthma events 15 to 42 days after vaccination. Similarly, in vaccine years 3 and 4, children who were 18 months to 4 years of age did not have a statistically significant increased risk for asthma events 15 to 42 days after vaccination. Also, LAIV-T did not increase the risk for asthma in children who received 1, 2, 3, or 4 annual doses of LAIV-T. Although the possibility for a true increased risk for asthma was observed in 1 of 4 years in children who were 18 months to 4 years at 15 to 42 days after vaccination, it is more likely that the association is a chance effect because of the 190 comparisons made without adjustment for multiple comparisons. We conclude that LAIV-T is safe in children who are 18 months to 4 years, 5 to 9 years, and 10 to 18 years of age. The hypothesis that LAIV-T is associated with an increase in asthma events in children who are younger than 5 years is not supported by our data. Reassessment of the lower age limit for use of LAIV-T in children is indicated.

Is influenza vaccination in asthma helpful?

PURPOSE OF REVIEW

Influenza infections are frequently involved in asthma exacerbations. During influenza epidemics substantial excess morbidity due to respiratory tract complications is reported in all age categories as well as excess mortality among the elderly. Vaccines are available for protection against influenza. Worldwide, vaccination is advised and considered a quality point for asthma care. However, the protective effect of influenza vaccination in patients with asthma is still disputed. In order to establish the current state of affairs we reviewed the recent literature on the protective effect of influenza vaccination and its usefulness in patients with asthma.

RECENT FINDINGS

Several studies were found addressing influenza and the protective aspects of vaccination. They discussed the incidence, the adverse effects of vaccination, the coverage of influenza vaccination among patients with asthma and the effectiveness of the vaccine.

SUMMARY

Influenza vaccination can safely be used in patients with asthma. Allegations that vaccination could provoke asthma exacerbations are convincingly invalidated by previous and recent research. Although patients with asthma are one of the major target groups for immunization, vaccine coverage in all age categories remains low. So far, no unequivocal beneficial effect of influenza vaccination in patients with asthma was found in observational and experimental studies in the sense of reduction of asthma exacerbations and other complications. Recent studies confirm these negative findings. More long-term randomized, placebo-controlled studies, focusing on influenza- proven illness in patients with asthma, are needed to address the question of how helpful influenza vaccination is in these patients.

Oral oseltamivir improves pulmonary function and reduces exacerbation frequency for influenza-infected children with asthma

BACKGROUND

Among asthmatic children, influenza is associated with increased hospitalizations. Although vaccination is safe and effective among asthmatic children, its protective efficacy varies and uptake rates can be low. In comparison, oseltamivir (Tamiflu) is effective against all influenza strains and can reduce the severity and duration of influenza among adults and children. This study determined the effects of oseltamivir among influenza-infected children with asthma.

METHODS

Asthmatic children (6-12 years of age) were randomized to receive oseltamivir (2 mg/kg) or placebo twice daily, as a syrup. The primary efficacy endpoint was the time to freedom from illness. Secondary endpoints included the area under the symptom score-hour curve, the proportion of patients with asthma exacerbations and changes in forced expiratory volume at 1 second during the dosing period. Analysis was performed for both the intent-to-treat infected (n = 179) and per protocol (n = 162) populations.

RESULTS

The primary endpoint for this study was not met. Oseltamivir tended to reduce the time to freedom from illness in the intent-to-treat infected population (10.4 hours, 8%; P = 0.5420), the per protocol population (24.3 hours, 17%; P = 0.1607) and patients who started treatment <24 hours after symptom onset (39.8 hours, 25%; P = 0.0780). However, an improvement in pulmonary function was observed. The improvement in forced expiratory volume at 1 second was significantly greater among oseltamivir-treated patients (10.8% versus 4.7%; P = 0.0148). Oseltamivir-treated patients also experienced fewer asthma exacerbations up to day 7 (68% versus 51%; P = 0.031). Oseltamivir was safe and well-tolerated.

CONCLUSIONS

Oseltamivir is safe and well-tolerated among asthmatic children, may reduce symptom duration and helps improve lung function and reduce asthma exacerbations during influenza infection.

Role of influenza vaccine for healthy children in the US

Influenza infection is associated with significant morbidity and mortality in adults, but the highest attack rates for influenza regularly occur in children, particularly those in preschool and elementary school. The consequences of influenza in this younger population - increased rate of hospitalization in those younger than 2 years of age and serious associated morbidity - have been underestimated. Children are also the critical link for spreading influenza in the community. Recent data suggest that mass influenza vaccination of healthy children would not only protect recipients, but also may reduce the burden of influenza throughout the community. During the past 3 decades, efforts to control influenza have focused on the use of an injectable trivalent inactivated vaccine (TIV) in high-risk persons. The vaccine is 'safe' and effective, but its acceptance and uptake by patients and healthcare providers have been modest at best. A new intranasal, live-attenuated, trivalent cold-adapted influenza virus vaccine (CAIV-T) [FluMist] is 'safe', well tolerated, immunogenic, and efficacious in preventing influenza illness in healthy children. Compared with TIV, CAIV-T is easier to administer and should be more readily acceptable, particularly for mass immunization campaigns. CAIV-T also induces a broader immune response and has demonstrated protection against at least three different variant influenza strains. This vaccine is particularly well suited for routine immunization of children and thus offers the potential for greatly improved control of influenza. However, the acquisition cost per single dose of FluMist for the 2003-4 season ( approximate, equals 46 US dollars) significantly hampered its uptake both by practitioners and by managed care organizations, even despite a later approximate, equals 25 US dollars rebate offer. For the 2004-5 season, CAIV-T is likely to be only modestly more expensive (average wholesale price: 16.50 US dollars for non-returnable doses, 23 US dollars for returnable doses) than TIV. The practitioner must consider the benefits of FluMist compared with its likely higher vaccine cost and the issues of reimbursement among multiple insurers.

Strong local and systemic protective immunity induced in the ferret model by an intranasal virosome-formulated influenza subunit vaccine

The proliferation of influenza viruses causes costly, recurrent, annual epidemics. Current vaccines, mainly administered parenterally, have been shown to be suboptimal in terms of efficacy, particularly where local IgA responses are concerned. Recent investigations of virosomes as delivery systems for viral HA and NA antigens have demonstrated an improved immune response. This paper investigates the efficacy of a novel virosome-based intranasal influenza vaccine by its ability to reduce disease symptoms and its effect on viral shedding in nasal secretions of immunised ferrets. The use of ferrets in the study of influenza vaccines is based on the good comparability between ferret and human response to the disease. Intranasal, as opposed to parenteral, administration of a trivalent virosome-based subunit vaccine adjuvanted with HLT provides an almost total prevention of virus shedding combined with a high level of immunological protection against homologous virus challenge. The ease of application of an intranasal vaccine may have positive repercussions in the adoption of influenza vaccinations, particularly in 'at-risk' groups.

Safety, immunogenicity and efficacy of intranasal, live attenuated influenza vaccine

Data supporting the use of the live attenuated influenza vaccine (LAIV) in children and adults is reviewed, and the development and characteristics of the vaccine are summarized. The vaccine is highly effective and well tolerated in children and adults from 5 to 49 years of age. Correlates of immune protection include serum hemagglutination-inhibition antibody and secretory immunoglobulin A. Efficacy against antigenically well-matched epidemic influenza strains was high at 92%. In 1 year, despite a significant antigenic change in the epidemic influenza virus that did not match the vaccine, LAIV conferred 86% protection against culture-confirmed illness in children. In the future it is expected that additional studies will support a broadening of the age range for use with the LAIV to prevent influenza in children and adults.

Trivalent Intranasal Influenza Vaccine, Live

OBJECTIVE

To review human data on the efficacy, safety, and clinical use of trivalent intranasal influenza vaccine, live (TIIVL).

DATA SOURCES

A MEDLINE search (1966–3rd week of January 2004) using the terms influenza vaccine, intranasal administration, and FluMist was conducted. References from pertinent articles were also reviewed.

STUDY SELECTION AND DATA EXTRACTION

Studies conducted in humans and published in English were selected. Double-blind, controlled trials evaluating the efficacy and safety of TIIVL were evaluated.

DATA SYNTHESIS

Administration of TIIVL results in mucosal and humoral immunity to influenza. Results of clinical trials in children and adults have demonstrated that TIIVL reduces the incidence of influenza. In children, TIIVL was also associated with a decrease in febrile illness and febrile otitis media. In adults, reductions in workday absences and medical visits due to febrile upper respiratory tract illness were also documented. TIIVL is well tolerated, with rhinorrhea or nasal congestion and sore throat occurring more frequently than with placebo.

CONCLUSIONS

TIIVL is an alternative to intramuscular inactivated influenza vaccine in healthy individuals between 5 and 49 years of age. However, the vaccine is contraindicated in the majority of patient populations for whom annual influenza vaccination is recommended. THIS ARTICLE IS APPROVED FOR CONTINUING EDUCATION CREDIT ACPE UNIVERSAL PROGRAM NUMBER: 407-000-04-037-H01

Immunizations, neonatal jaundice, and animal-induced injuries

PURPOSE OF REVIEW

Published studies during the past year about three topics important to the pediatric clinician-- immunizations, neonatal jaundice, and animal-induced injuries-are concisely reviewed.

RECENT FINDINGS

Recent updates regarding vaccines including the questionable link with autism, implementation of universal influenza vaccination for young children, the efficacy of pneumococcal vaccine against invasive disease, and new information on pertussis, varicella, hepatitis A, hepatitis B, measles, and rotavirus vaccination are discussed. No association between measles/mumps/rubella vaccine or thimerosal-containing pertussis vaccine and autism is evident. Universal influenza vaccination for children 6 to 23 months of age will be recommended for the 2004-2005 flu season, and this implementation should reduce significant school absenteeism as well as complications seen last year including encephalopathy, seizures, respiratory failure, and pneumonia. Pneumococcal vaccine significantly reduces rates of invasive pneumococcal vaccine in healthy and HIV-infected children, although it does not appear to greatly affect otitis media rates. A reduction in post-vaccine febrile seizures appears to be present since the introduction of acellular pertussis vaccine. Multiple outbreaks in varicella have been reported since the introduction of the varicella vaccine, and a booster vaccination may be necessary in the future. Methods for detecting and preventing severe neonatal hyperbilirubinemia are reviewed, as well as anticipated recommendations from the American Academy of Pediatrics for the detection and management of hyperbilirubinemia. High bilirubin levels in preterm infants may result in hearing dysfunction and developmental impairment. The American Academy of Pediatrics has recommended a higher level of monitoring for newborn jaundice and treatment of hyperbilirubinemia in an effort to prevent kernicterus and sequelae from elevated bilirubin levels, including post-discharge follow-up appointment by day 3 to 5 of age. Dog bites in children with resultant post-traumatic stress disorder, rabies, and salmonellosis from pet reptiles in the home are also addressed. Clinicians need to be aware of the risk for rabies bites, need to recognize that dog bites in children appear to cause post-traumatic stress disorder in more than half of cases, and need to know how to educate patients on how to prevent salmonellosis from pet reptiles and amphibians.

SUMMARY

Progress has been made in immunizations, especially immunization for influenza, pneumonia, and pertussis. It is recommended that monitoring for neonatal hyperbilirubinemia be more thorough to prevent the consequences of this condition. Rabies, post-traumatic stress disorder from dog bites, and salmonellosis associated with pet reptiles constitute an important area for patient education.

Current status of live attenuated influenza virus vaccine in the US

The efficacy and effectiveness of cold adapted live attenuated (CAIV-T, FluMist intranasal influenza vaccine is reviewed. CAIV-T consists of approximately 10(7) TCID50 per dose of each influenza A/H1N1, influenza A/H3N2, and influenza B vaccine strain. The exact strains are updated each year to antigenically match the antigens recommended by national health authorities for inclusion in the vaccine. In one year in which the vaccine strain did not well match the epidemic strain, the live attenuated vaccine induced a broad immune response that cross-reacted significantly with the drifted strain. The efficacy of CAIV-T in adults was demonstrated with challenge studies and the effectiveness of the vaccine for reducing febrile upper respiratory illness, days of missed work, and days of antibiotic use was demonstrated in a large field trial. In young children, protective efficacy against culture confirmed influenza was demonstrated in a field trial with overall protective efficacy of 92% during a two year study. Vaccine was also highly protective against a strain not contained in the vaccine, with 86% protective efficacy demonstrated against this significantly drifted virus. Effectiveness measures, including protection against febrile otitis media and visits to the doctor were demonstrated. Live attenuated vaccine provides a significant new tool to help prevent influenza.

Comparison of immunogenicity and tolerability of a virosome-adjuvanted and a split influenza vaccine in children

OBJECTIVE

To compare the immunogenicity and safety of a virosome-adjuvanted influenza vaccine (Inflexal V; Berna Biotech, Berne, Switzerland) and a split influenza vaccine (Fluarix; GlaxoSmithKline Biologicals, Rixensart, Belgium) in children.

SUBJECTS AND METHODS

The subjects, 453 children ages 6 to 71 months, were stratified into primed and unprimed and age groups (6 to 35 and 36 to 71 months) and then randomized 1:1 to receive virosome-adjuvanted (n = 224) or split influenza vaccine (n = 229), a half or full dose was given intramuscularly according to age. Unprimed children received a second dose after 4 weeks. Blood samples (n = 326) collected pre-and 28 days postvaccination were analyzed by hemagglutination inhibition test. Safety assessments were made at baseline and follow-up visits by the investigators and by parents for the 4 days after vaccinations.

RESULTS

Both vaccines induced an effective immune response. Seroconversion rates (>4-fold titer rise) against the WHO recommended strains A/New Caledonia (H3N2), A/Moscow (H1N1) and B/Hongkong (B) were 80.1, 66.0 and 90.4% for the virosome-adjuvanted and 75.9, 62.9 and 89.4% for the split influenza vaccine, respectively. Unprimed children's seroconversion rates for H3N2 were significantly higher (P = 0.02) for the virosome-adjuvanted (88.8%) than for split influenza vaccine (77.5%). Seroprotection rates (titer of > 40) for H3N2, H1N1 and B, respectively, were 87.8, 80.1 and 90.4% after vaccination with the virosome-adjuvanted vaccine and 82.9, 78.2 and 89.4% after the split influenza vaccine. Unprimed children's seroprotection rate was significantly higher (P = 0.03) for H3N2 after the virosome-adjuvanted (88.8%) than those for the split influenza vaccine (78.3%). Equivalent geometric mean titer fold increases were evident for both vaccines. No serious adverse events were seen. Pain/ tenderness, redness and swelling/induration was found in 25.4, 11.2 and 8.9% for the virosome-adjuvanted vaccine and in 24.0, 9.2 and 6.1% for the split influenza vaccine, respectively. The rates of fever, malaise/irritability and shivering was 6.3, 11.6 and 2.7% for the virosome-adjuvanted vaccine and 8.3, 11.8 and 2.6% for the split influenza vaccine, respectively.

CONCLUSIONS

The virosome-adjuvanted influenza vaccine showed greater immunogenicity over the split influenza vaccine in unprimed children and showed a trend toward better immunogenicity in the rest of the study population. Both vaccines were well-tolerated.

Safety and efficacy of influenza vaccine in children

OBJECTIVE

To describe the safety and efficacy of influenza vaccines in asthmatic children.

DATA SOURCES

Literature was identified by a MEDLINE search (2002-March 2003). Key search terms included asthma, exacerbation, children, vaccine, and influenza.

DATA SYNTHESIS

Concerns that the influenza vaccine may exacerbate asthma attacks have kept many asthmatic children from receiving this immunization. Researchers have conducted studies to determine the burden of influenza on asthmatic children, the safety of influenza vaccines, and their benefit in the presence of glucocorticoid burst therapy in the same population.

CONCLUSIONS

Influenza vaccines tested are safe and efficacious in asthmatic children.

Safety and efficacy of live attenuated, cold-adapted, influenza vaccine-trivalent

This article describes the efficacy, immunogenicity, and safety of CAIV-T. This vaccine has the potential to significantly contribute to the control of influenza infection and influenza-associated illnesses, including febrile otitis media and lower respiratory disease. When compared with inactivated vaccine, CAIV-T has significant advantages in convenience of administration. The high efficacy of CAIV-T and its efficacy in children against a significantly drifted strain of H3N2 (A/Sydney), a strain not contained in the vaccine, are compelling observations for use of the vaccine in children. Effectiveness in adults was demonstrated using the same vaccine strain against the drifted H3N2 strain. The proposed vaccine administration schedule for healthy individuals aged 9 to 49 years is a single dose administered annually before the winter. For children aged 5 to 8 years, two doses are recommended the first year they are immunized with CAIV-T to ensure protection against all strains contained in the vaccine. Thereafter, a single annual revaccination is sufficient.

Are we ready for universal influenza vaccination in paediatrics?

Recent studies have suggested that paediatric influenza is a greater medical problem than usually thought because it can cause excess hospitalisations, medical visits, and antibiotic prescriptions even in healthy children, especially those under 2 years. Furthermore, influenza in otherwise healthy children may have substantial socioeconomic consequences for the children and their household contacts. These findings have led many experts to encourage the more widespread use of influenza vaccine in childhood. Although the immunogenicity of the available vaccines is good and they are safe, well-tolerated, and highly effective in preventing influenza and its complications, economic data support universal vaccination only when indirect effectiveness is considered. However, infants aged 6-23 months, children with recurrent acute otitis media or respiratory-tract infections, and healthy children attending day-care centres or elementary schools should be included among the paediatric groups requiring vaccination.

Every nose counts: a new influenza vaccine for all healthy schoolchildren?

Influenza is a vaccine-preventable disease. However, influenza virus spreads among children in schools and daycare centers, then to families and communities, causing uncontrolled epidemics every winter. The United States Food and Drug Administration evaluated and approved an investigational live-attenuated, cold-adapted, trivalent influenza vaccine for licensure, for prevention of influenza in healthy children and healthy adults, 5 through 49 years of age. Could protection of healthy schoolchildren against influenza limit its spread and benefit society?

Vaccines for preventing influenza in people with asthma

BACKGROUND

Influenza vaccination is recommended for asthmatic patients in many countries as observational studies have shown that influenza infection can be associated with asthma exacerbations, but influenza vaccination itself has the potential to adversely affect pulmonary function. A recent overview concluded that there was no clear benefit of influenza vaccination in patients with asthma but this conclusion was not based on a systematic search of the literature.

OBJECTIVES

Whilst influenza may cause asthma exacerbations, there is controversy about the use of influenza vaccinations, since they may precipitate an asthma attack in some people. The objective of this review was to assess the efficacy of influenza vaccination in children and adults with asthma.

SEARCH STRATEGY

We searched the Cochrane Airways Group trials register and checked reference lists of articles. The last search was carried out in February 2003.

SELECTION CRITERIA

Randomised trials of influenza vaccination in children (over two years of age) and adults with asthma. Studies involving people with chronic obstructive pulmonary disease were excluded.

DATA COLLECTION AND ANALYSIS

Inclusion criteria and assessment of trial quality were applied by two reviewers independently. Data extraction was done by two reviewers independently. Study authors were contacted for missing information.

MAIN RESULTS

Nine trials were initially included. Four of these trials were of high quality. Five further articles have been included in two updates (Bueving 2002; Castro 2001; Redding 2002; Reid 1998). The included studies covered a wide diversity of people, settings and types of influenza vaccination, but data from the more recent studies that used similar vaccines have been pooled. The pooled results of two trials involving 2306 people with asthma did not demonstrate a significant increase in asthma exacerbations in the two weeks following influenza vaccination (Risk Difference 0.00; 95% confidence interval -0.02 to 0.02). A recent study on 696 children with asthma did not demonstrate a significant reduction in influenza related asthma exacerbations (Risk Difference 0.01; 95% confidence interval -0.02 to 0.04).

REVIEWERS' CONCLUSIONS

Evidence from recently published trials indicates that there is no significant increase in asthma exacerbations immediately after vaccination (at least with inactivated influenza vaccination); however, uncertainty remains about the degree of protection vaccination affords against asthma exacerbations that are related to influenza infection.