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Direct and Indirect Protection with Pediatric Quadrivalent Live-Attenuated Influenza Vaccination in Europe Estimated
Laetitia Gerlier1, Judith Hackett2, Richard Lawson2
1QuintilesIMS, Real-World Evidence Solutions, Zaventem, Belgium.
Insights
Annual vaccination of children with quadrivalent live-attenuated influenza vaccine (QLAIV) in Europe significantly reduces symptomatic influenza cases. This strategy offers substantial direct and indirect protection across diverse populations and vaccination coverages.
Area of Science:
- Epidemiology
- Public Health
- Vaccinology
Background:
- Influenza remains a significant public health concern in Europe.
- Current vaccination strategies utilize quadrivalent inactivated vaccines (QIV).
- Live-attenuated influenza vaccines (LAIV) offer an alternative for pediatric immunization.
Purpose of the Study:
- To estimate the public health impact of annual pediatric vaccination with quadrivalent live-attenuated influenza vaccine (QLAIV) across Europe.
- To compare the impact of QLAIV against current QIV vaccination coverage.
- To assess both direct and indirect protection conferred by QLAIV.
Main Methods:
- A deterministic, age-structured, dynamic transmission model simulated influenza across 14 European countries.
- The model compared current QIV coverage to a scenario of 50% QLAIV coverage in children aged 2-17.
- Vaccine efficacy, immunity duration, and reproduction number (R0) were key parameters, with sensitivity analyses performed.
Main Results:
- Annual QLAIV vaccination in children could prevent an average of 2495 symptomatic cases per 100,000 population over 10 years.
- This represents a 47.6% reduction compared to QIV-only vaccination.
- Significant indirect protection was observed in adults, preventing an average of 1466 cases per 100,000 population.
Conclusions:
- Pediatric vaccination with QLAIV provides substantial direct and indirect public health benefits in Europe.
- The model highlights the importance of vaccine efficacy, immunity duration, and transmission dynamics (R0).
- Expanding pediatric vaccination with QLAIV is a promising strategy for influenza control across diverse European settings.
Abstract:
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.
