This study is open-label, randomized and controlled phase Ⅳ clinical trial of quadrivalent influenza vaccine.The purpose of this study is to compare the immunogenicity and safety after 1 dose of quadrivalent influenza vaccine with that of 2 doses in vaccine-unprimed children aged 3-8 years old,to compare the immunogenicity and safety after 1 dose of quadrivalent influenza vaccine in vaccine-unprimed children aged 3-8 years old with that of 1 dose in vaccine-primed children and to compare the immunogenicity and safety after 2 doses of quadrivalent influenza vaccine in vaccine-unprimed children aged 3-8 years old with that of 1 dose in vaccine-primed children.A total of 600 subjects including 400 vaccine-unprimed children and 200 vaccine-primed children will be enrolled,400 vaccine-unprimed children will be randomly divided into two groups in a 1:1 ratio.Subjects in group 1(experimental group 1 ) will receive two doses of quadrivalent influenza vaccine on the immunization schedule of day 0,28 and subjects in group 2 (experimental group 2) will receive one dose of quadrivalent influenza vaccine.200 vaccine-primed children (experimental group 3) will receive one dose of quadrivalent influenza vaccine.
This is an open-label, randomized and controlled phase Ⅳ clinical trial of quadrivalent influenza vaccine manufactured by Sinovac Biotech Co. , the purpose of this study is to compare the immunogenicity and safety after 1 dose of quadrivalent influenza vaccine with that of 2 doses in vaccine-unprimed children aged 3-8 years old,to compare the immunogenicity and safety after 1 dose of quadrivalent influenza vaccine in vaccine-unprimed children aged 3-8 years old with that of 1 dose in vaccine-primed children and to compare the immunogenicity and safety after 2 doses of quadrivalent influenza vaccine in vaccine-unprimed children aged 3-8 years old with that of 1 dose in vaccine-primed children.