Influenza Vaccine Effectiveness in Mainland China: A Systematic Review and Meta-Analysis.

Influenza endangers human health but can be prevented in part by vaccination. Assessing influenza vaccine effectiveness (VE) provides scientific evidence for developing influenza vaccination policy. We conducted a systematic review and meta-analysis of studies that evaluated influenza VE in mainland China. We searched six relevant databases as of 30 August 2019 to identify studies and used Review Manager 5.3 software to analyze the included studies. The Newcastle-Ottawa scale was used to assess the risk of publication bias. We identified 1408 publications, and after removing duplicates and screening full texts, we included 21 studies in the analyses. Studies were conducted in Beijing, Guangzhou, Suzhou, and Zhejiang province from the 2010/11 influenza season through the 2017/18 influenza season. Overall influenza VE for laboratory confirmed influenza was 36% (95% CI: 25-46%). In the subgroup analysis, VE was 45% (95% CI: 18-64%) for children 6-35 months who received one dose of influenza vaccine, and 57% (95% CI: 50-64%) who received two doses. VE was 47% (95% CI: 39-54%) for children 6 months to 8 years, and 18% (95% CI: 0-33%) for adults ≥60 years. For inpatients, VE was 21% (95% CI: -11-44%). We conclude that influenza vaccines that were used in mainland China had a moderate effectiveness, with VE being higher among children than the elderly. Influenza VE should be continuously monitored in mainland China to provide evidence for policy making and improving uptake of the influenza vaccine.