[Studies on re-immunization with live attenuated hepatitis A vaccine]

The possibility of re-immunization with a booster dose of live attenuated hepatitis A (HA) vaccine was studied.

Children randomly sampled were divided into three groups with re-immunization, primary immunization and immunity via natural infection. Antibodies against hepatitis A virus (anti-HAV) were detected qualitatively and quantitatively with modified Abbott enzyme immunoassay (EIA).

Proportion of children with positive anti-HAV and its mean geometric titer (GMT) increased within two weeks after re-immunization, and as compared, those increased slowly and GMT reached the peak three months after primary immunization. Response to the live attenuated vaccine differed between the groups of re-immunization and immunity via natural infection, and should be taken into consideration in studying immune persistence of the vaccine. Proportion of children, who converted negative of their anti-HAV after primary immunization, with positive anti-HAV after re-immunization was 83.3% (10/12), significantly higher than that in those who failed in primary immunization and then were vaccinated again (50%, with 17/34), and that in both of them were higher than in primary immunization (29.6%).

Reminiscence could be induced by re-immunization, and the effects of it depended on primary immunization. Detection of anti-HAV with modified Abbott EIA still underestimated primary immune reaction. A more sensitive and specific method for detecting anti-HAV after vaccination should be used.