Subjects receive 2 dosed of quadrivalent influenza vaccine 4 weeks apart.Blood samples were obtained from children at 3 time points-before receiptof dose 1, 4 weeks after receipt of dose 1 and before dose 2, and 4 weeksafter dose 2. Hemagglutination inhibition (HAI) antibody titers to the A/H3N2,A/H1N1, and B antigens included in the vaccine were measured at each timepoint
Routine annual influenza vaccination is recommended for all persons aged≥6 months who do not have contraindications. For those aged 6 monthsthrough 8 years who have previously received ≥2 total doses of trivalent orquadrivalent influenza vaccine ≥4 weeks apart, they require only 1 dose ofinfluenza vaccine. For those who have not previously received ≥2 doses oftrivalent or quadrivalent influenza vaccine, they require 2 dose of influenzavaccine. but the evidence on how to select vaccine doses for quadrivalentinfluenza vaccine is limited in China. The study is a prospective, open-labelcomparison of the immunogenicity and reactogenicity of 1 versus 2 doses ofan inactivated quadrivalent influenza vaccine in subjects of 3-8 years old withdifferent history of influenza vaccination.