Objective To evaluate the incidence of seasonal influenza among unvaccinated individuals.Methods Foreign databases including the National Library of Medicine,Cochrane Library,and ClinicalTrials.gov,as well as Chinese databases such as the China Biomedical Literature Database,China Journal Full-text Database,and Wanfang Data were searched.Randomized controlled trials(RCTs)assessing the incidence of laboratory-confirmed influenza in placebo groups receiving seasonal influenza vaccines were included in the analysis.The study calculated the incidence rates of symptomatic influenza and the combined incidence rates of both symptomatic and asymptomatic influenza in unvaccinated populations.Meta-analysis was conducted using STATA 13.0.Results A total of 32 RCTs were included.The pooled incidence rates of symptomatic influenza were 14％for individuals＜18 years,4％for individuals aged 18-64 years,and 7％for individuals ≥ 65 years.The incidence rates of symptomatic and asymptomatic influenza were 25％for individuals＜18 years,and 11％for individuals aged 18-64 years.Conclusions Among individuals not receiving the seasonal influenza vaccine,the incidence of influenza significantly differs across age groups,with higher incidence rates observed in children and the elderly.
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