Influenza vaccine (split virion, quadrivalent)(Anhui Zhifei Longcom Biopharmaceutical)

Primary objective: To evaluate the immunogenicity of children aged 6-35 months who received 2 doses of high-dose experimental vaccine (0.5 ml/dose) or low-dose experimental vaccine (0.25 ml/dose) on a 0- and 28-day schedule, 30 days after the full vaccination. Secondary objective: To evaluate the safety of children aged 6-35 months who received 2 doses of high-dose experimental vaccine (0.5 ml/dose) or low-dose experimental vaccine (0.25 ml/dose) on a 0- and 28-day schedule.

Primary objective: To investigate the safety of different doses of quadrivalent influenza virus split vaccine in people aged 6 to 35 months. Immunogenicity Exploratory objective (applicable to Phase II): To investigate the immunogenicity of different doses of quadrivalent influenza virus split vaccine in people aged 6 to 35 months.