Abstract:
Objective To evaluate the vaccine effectiveness (VE) of trivalent inactivated influenza vaccine (TIV) against influenza among primary school students in Longgang district, Shenzhen city, Guangdong province during the 2024–2025 academic year, thus providing evidence for the cost-effectiveness evaluation of publicly funded influenza vaccine (InfV) programs.
Methods Data on the roster of in-school primary school students in Longgang district from August 2024 to July 2025, together with their influenza incidence and InfV vaccination records, were extracted from the Longgang District Student Health Monitoring Information System, the China Information System for Disease Control and Prevention, and the Shenzhen Immunization Program Information Management System. According to class-level InfV vaccination coverage, students were stratified into four groups: <50.00%, 50.00%–74.99%, 75.00%–100%, and an overall group. Propensity score matching (PSM) was employed to balance covariates between the TIV-vaccinated and unvaccinated groups, forming a comparable real-world retrospective cohort. Multivariable Cox regression models were employed to estimate the adjusted vaccine effectiveness (aVE) of TIV against influenza.
Results After PSM, the overall group comprised 159 336 participants in both the TIV-vaccinated and unvaccinated groups, with influenza incidence densities of 1.40 and 2.35 per 100 person-years, respectively. The aVE (95%CI) of TIV against influenza by class-level vaccination coverage was 29.83% (21.00% to 37.67%) for the < 50.00% group, 37.84% (31.39% to 43.67%) for the 50.00%–74.99% group, 41.06% (36.23% to 45.53%) for the 75.00%–100% group, and 40.31% (36.44% to 43.95%) for the overall group. By age subgroups, the aVE (95%CI) was 46.75% (42.22% to 50.93%) for students of 6 to 8 years old and 28.76% (21.34% to 35.48%) for students of 9 to 12 years old. By vaccination history, the aVE (95%CI) was 46.52% (41.15% to 51.40%) for those unvaccinated the previous year and 35.78% (30.20% to 40.92%) for those vaccinated previously. Against influenza A, B, and mixed A+B, the aVE (95%CI) was 42.33% (37.48% to 46.80%), 35.64% (23.43% to 45.90%), and 21.00% (−22.46% to 49.04%), respectively.
Conclusions TIV vaccination conferred substantial protective effects against influenza among primary school students in Longgang district during the 2024–2025 academic year. Annual timely administration of InfV before the influenza epidemic season and maintenance of high vaccination coverage are recommended.
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