Safety Profiles of Seasonal Influenza Vaccines in Chinese Children and Adolescents: A Pooled Analysis of Five Clinical Studies

INTRODUCTION: Safety concerns remain an important barrier to pediatric influenza vaccination, yet directly comparable evidence across vaccine platforms, valency formulations, and administration routes remains limited. This study compared the safety profiles of five seasonal influenza vaccines in Chinese children and adolescents. METHODS: We pooled individual-level safety data from five clinical studies including participants aged 6-17 years. Adverse event (AE) incidences and 95% confidence intervals (CIs) were estimated using Clopper-Pearson methods, and multivariable logistic regression models were used to compare AE risks. RESULTS: Among 2885 participants, overall AE incidence was 23.1% (95% CI, 21.6-24.7%). Grade 3 AEs were uncommon (≤ 1.1%), and no serious AEs were reported. AE profiles differed across vaccine platforms: inactivated vaccines were mainly associated with pyrexia and injection-site reactions, whereas trivalent live attenuated influenza vaccine was characterized by rhinorrhea, cough, and nasal congestion. Compared with trivalent inactivated split-virion vaccine, quadrivalent inactivated subunit vaccine was associated with lower odds of any AE (aOR, 0.52; 95% CI, 0.35-0.79) and local AEs (aOR, 0.30; 95% CI, 0.17-0.52). CONCLUSIONS: All five vaccines showed acceptable short-term safety, with platform-specific reactogenicity patterns. Among inactivated vaccines, the quadrivalent subunit formulation showed a relative local tolerability advantage.