Influenza vaccine efficacy in young children attending childcare: A randomised controlled trial

Efficacy and effectiveness of influenza vaccination in healthy children. A review of current evidence

Influenza is common in healthy children and adolescents and is associated with a high rate of hospitalization in this group, especially for those <5 years. Although the WHO has recommended vaccination in children under 5 years of age since 2012, it is really implemented in few countries today. The aim of this paper was to review the available evidence on the efficacy/effectiveness of influenza vaccination in healthy children <18 years of age through a non-systematic search of studies conducted between 2010 and 2020. Despite the high variability in results due to differences in design, vaccine type and season included in the 41 selected studies, statistically significant studies show efficacy values for the influenza vaccine of between 25.6% and 74.2%, and effectiveness from 26% to 78.8%. Although a systematic review would be necessary to corroborate the evidence, this review suggests that paediatric vaccination is generally an effective measure for preventing influenza in healthy children in line with international organisms' recommendations.

Clinical endpoints to inform vaccine policy: A systematic review of outcome measures from pediatric influenza vaccine efficacy trials

INTRODUCTION

We conducted a systematic review of pediatric influenza vaccine efficacy trials to assess clinical outcome measures and whether the trials defined important public health endpoints.

MATERIAL AND METHODS

We systematically identified phase 3 or 4 influenza vaccine randomized controlled trials among children ≤18 years of age with laboratory-confirmed influenza outcomes since 1980. We recorded countries, age groups, vaccine formulations, specimen collection criteria, laboratory diagnostics, primary and secondary outcome measures, and funders, and we determined income category for study countries. We used descriptive statistics to summarize study characteristics. We analyzed the studies overall and a subset of studies conducted in at least one low- and middle-income country (LMIC).

RESULTS

From 6455 potentially relevant articles, we identified 41 eligible studies. Twenty-one studies (51%) were conducted in at least one LMIC, while the remaining studies (49%) were conducted in high-income countries only. Thirty-one studies (76%) included children younger than six years. We found 40 different primary outcome measures among the 41 eligible studies. Thirty-three studies (80%) reported standardized symptoms or findings which defined a primary outcome or triggered specimen collection. One study defined a primary outcome which captured more severe illness; however, cases were mostly due to high body temperature without other severity criteria. Of the 21 studies from at least one LMIC, 15 (71%) were published since 2010 and 17 (81%) enrolled children younger than six years. Eighteen (86%) studies from at least one LMIC reported standardized symptoms or findings which defined a primary outcome or triggered specimen collection.

CONCLUSIONS

Among pediatric influenza vaccine efficacy trials, primary outcome measures and clinical specimen collection criteria were highly variable and, with one exception, focused on capturing any influenza illness. As most LMICs do not have influenza vaccination programs, our study highlights a potential data limitation affecting policy and implementation decisions in these settings.

Repeat Dosing of AAV2.5T to Ferret Lungs Elicits an Antibody Response That Diminishes Transduction in an Age-Dependent Manner

Readministration of recombinant adeno-associated virus (rAAV) may be necessary to treat cystic fibrosis (CF) lung disease using gene therapy. However, little is known about rAAV-mediated immune responses in the lung. Here, we demonstrate the suitability of the ferret for testing AAV2.5T-mediated CFTR delivery to the lung and characterization of neutralizing-antibody (NAb) responses. AAV2.5T-SP183-hCFTRΔR efficiently transduced both human and ferret airway epithelial cultures and complemented CFTR Cl^– currents in CF airway cultures. Delivery of AAV2.5T-hCFTRΔR to neonatal and juvenile ferret lungs produced hCFTR mRNA at 200%–300% greater levels than endogenous fCFTR. Single-dose (AAV2.5T-SP183-gLuc) or repeat dosing (AAV2.5T-SP183-fCFTRΔR followed by AAV2.5T-SP183-gLuc) of AAV2.5T was performed in neonatal and juvenile ferrets. Repeat dosing significantly reduced transgene expression (11-fold) and increased bronchoalveolar lavage fluid (BALF) NAbs only in juvenile, but not neonatal, ferrets, despite near-equivalent plasma NAb responses in both age groups. Notably, both age groups demonstrated a reduction in BALF anti-capsid binding immunoglobulin (Ig) G, IgM, and IgA antibodies after repeat dosing. Unique to juvenile ferrets was a suppression of plasma anti-capsid-binding IgM after the second vector administration. Thus, age-dependent immune system maturation and isotype switching may affect the development of high-affinity lung NAbs after repeat dosing of AAV2.5T and may provide a path to blunt AAV-neutralizing responses in the lung.

Self-collected compared with professional-collected swabbing in the diagnosis of influenza in symptomatic individuals: A meta-analysis and assessment of validity

Self-collected nasal swabs offer a cheaper alternative to professional-collected swabs for influenza testing. However, the diagnostic accuracy of self-collection has not been quantitatively reviewed. We identified 14 studies that compared diagnostic accuracy of self-collected to professional-collected swabs in influenza symptomatic individuals. Self-collected swabs were found to be highly acceptable, simple and comfortable to use. Data from nine studies were meta-analyzed. Pooled sensitivity was 87% (95% CI: 80%, 92%) and specificity was 99% (95% CI: 98%, 100%), compared to professional-collected swabs in the diagnosis of influenza. Pooled sensitivity and specificity estimates were used to assess the potential bias that would be introduced in studies had self-collected rather than professional-collected samples been used. While self-collected swabbing should not replace the role of clinical testing, our findings support the use of self-collected swabs for influenza research and surveillance. This method will be an important tool for evaluating novel influenza vaccines and vaccination strategies.

A trivalent, inactivated influenza vaccine (Vaxigrip®): summary of almost 50 years of experience and more than 1.8 billion doses distributed in over 120 countries

INTRODUCTION

Vaxigrip, a trivalent split-virion, inactivated vaccine available since 1968 has been in use longer than any other influenza vaccine. It is the most widely-used influenza vaccine, with more than 1.8 billion doses distributed in more than 120 countries. Areas covered: The significant body of evidence that confirms the efficacy, effectiveness, immunogenicity, and safety of Vaxigrip in healthy individuals of all ages and at-risk populations is summarized. The results from at least 15 randomized efficacy trials and 15 other studies have demonstrated that vaccination with Vaxigrip is efficacious against various clinical endpoints. It was estimated that more than 37 million laboratory-confirmed influenza episodes, 476,000 influenza-related hospitalizations, and 67,000 influenza-related deaths have been avoided by the more than 1.8 billion doses of Vaxigrip that have been distributed, emphasizing its important public health impact. Expert commentary: This strong evidence base in favor of Vaxigrip provides a robust foundation to support the implementation of the quadrivalent formulation. This quadrivalent formulation of Vaxigrip contains two A and two B influenza strains (VaxigripTetra), and has a similar immunogenicity and safety profile to the trivalent formulation while offering broader protection due to the addition of the second influenza B strain.