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

Objectives We estimated the epidemiological and economic impact of extending the French influenza vaccination programme from at-risk/elderly (>= 65 years) only to healthy children (2-17 years). Methods A deterministic, age-structured, dynamic transmission model was used to simulate the transmission of influenza in the French population, using the current vaccination coverage with trivalent inactivated vaccine (TIV) in at-risk/elderly individuals (current strategy) or gradually extending the vaccination to healthy children (aged 2-17 years) with intranasal, quadrivalent live-attenuated influenza vaccine (QLAIV) from current uptake up to 50% (evaluated strategy). Epidemiological, medical resource use and cost data were taken from international literature and country-specific information. The model was calibrated to the observed numbers of influenza-like illness visits/year. The 10-year number of symptomatic cases of confirmed influenza and direct medical costs ('all-payer') were calculated for the 0-17-(direct and indirect effects) and >= 18-year-old (indirect effect). The incremental cost-effectiveness ratio (ICER) was calculated for the total population, using a 4% discount rate/year. Results Assuming 2.3 million visits/year and 1960 deaths/year, the model calibration yielded an all-year average basic reproduction number (R-0) of 1.27. In the population aged 0-17 years, QLAIV prevented 865,000 influenza cases/year (58.4%), preventing 10-year direct medical expenses of (sic)374 million. In those aged >= 18 years with unchanged TIV coverage, 1.2 million cases/year were averted (27.6%) via indirect effects (additionally prevented expenses, (sic)457 million). On average, 613 influenza-related deaths were averted annually overall. The ICER was (sic)18,001/life-year gained. The evaluated strategy had a 98% probability of being cost-effective at a (sic)31,000/life-year gained threshold. Conclusions The model demonstrated strong direct and indirect benefits of protecting healthy children against influenza with QLAIV on public health and economic outcomes in France.