Influenza virus vaccine(Hualan Biological Bacterin Co., Ltd.)

Primary objectives: To evaluate the protective efficacy of influenza virus split vaccine (15μg/subtype/0.5ml/dose) (hereinafter referred to as "influenza vaccine") in preventing laboratory-confirmed influenza cases (nucleic acid detection RT-qPCR method) in people aged 9-59 years and ≥60 years 14 days after a single dose during an influenza epidemic season. Secondary objectives: (1) To evaluate the protective efficacy of influenza vaccine in preventing laboratory-confirmed severe influenza cases (nucleic acid detection RT-qPCR method) in people aged 9-59 years and ≥60 years 14 days after a single dose during an influenza epidemic season. (2) To evaluate the protective efficacy of influenza vaccine in preventing laboratory-confirmed influenza cases (virus culture detection method) with a matching vaccine strain in people aged 9-59 years and ≥60 years 14 days after a single dose during an influenza epidemic season. (3) To evaluate the safety of influenza vaccine in people aged 9-59 years and ≥60 years. Exploratory objectives: (1) To evaluate the immunogenicity of influenza vaccine at 30 days after a single dose in people aged 9-59 years and ≥60 years. To explore the correlation between the protective efficacy and immunological indicators of different populations and subtypes. (2) To evaluate the immune persistence of influenza vaccine at 180 days after a single dose in people aged 9-59 years and ≥60 years.