Seasonal influenza vaccination rate and vaccine effectiveness among older adults in mainland China: a systematic review and meta-analysis.

Introduction: Both vaccine coverage and its effectiveness determine the influence of seasonal influenza vaccination on influenza control within a population. We conducted a systematic review and meta-analysis to estimate the influenza vaccination rate (IVR) and vaccine effectiveness (VE) among older adults in mainland China.

Methods: We searched five databases for the last 12 years, selecting studies that included people aged 60 years or older in mainland China. Random or fixed effects models were used to generate summary IVR and VE. The heterogeneity was assessed by subgroup analyses and meta-regression. Potential biases of the included studies were examined using the Agency for Healthcare Research and Quality Inventory and the Newcastle-Ottawa Scale.

Results: For IVR, we included 65 studies, involving 149 458 672 participants. The overall pooled IVR was found to be 17% (95% CI: 14%-21%), with lower IVRs observed in areas lacking free vaccination policies (7%, 95% CI: 5%-9%) and among individuals with chronic diseases (13%, 95% CI: 8%-19%). To assess VE against laboratory-confirmed influenza, we included 14 studies, involving 13 950 participants. The overall pooled VE was 33% (95% CI: 10%-51%), with a higher VE estimate observed for influenza A(H1N1) pdm09 (51%, 95% CI: 13%-73%) and when the vaccine matched the circulating virus strain (37%, 95% CI: 9%-56%).

Conclusions: IVRs among older adults in the included areas are low, especially among those lacking access to free policies and those with chronic diseases. Furthermore, the current vaccine provides low protection. It is crucial to increase influenza vaccination uptake and develop more effective vaccines for older adults.