Investigation and analysis of antibody levels of hepatitis A among children before and after implementing the Expanded National Immunization Program in China.

Objective: To analyze changes of hepatitis A antibody levels and immunization coverage of HAV vaccine among children before and after implementing the Expanded National Immunization Program in five counties of China, and to provide evidence for developing hepatitis A vaccine immunization strategies.

Methods: 449 children born in 2001, 2005 and 2009 were selected from five counties for an immunization coverage and a sero-prevalence survey of hepatitis A. The chemiluminescence microparticle immunoassays (CMIA) were used to detect hepatitis A IgG antibody and analyzed the factors which influenced the immunization coverage and positive rates.

Results: Among 449 subjects of children born in 2001, 2005 and 2009, the immunization coverage were 53.02%, 78.52% and 99.34% (χ = 91.285, P < 0.001). The positivity rates of hepatitis A IgG antibody were 61.07%, 81.21%, 95.36% (χ = 54.198, P < 0.001), respectively. The immunization coverage and positivity rate significantly increased with the delay of birth year. Children accepting different doses of HA vaccines are significantly different in positive rates of HA antibody, while there are no significant differences of different genders, years of birth, residence types, or types of registered permanent residence in different regions. The positivity rate increased significantly with administration of hepatitis A vaccine and shorter intervals between sample collection and HAV immunization.

Conclusions: After the Expanded National Immunization Program was implemented, hepatitis A antibody levels were significantly increased in five counties, which indicates a successful result of EPI.