[Further survey on efficacy of attenuated live hepatitis A vaccines]

To further survey the protective efficacy of the standard attenuated live hepatitis A vaccines (H(2) strain).

Randomized and controlled trials were performed in Fucheng county, Hebei province. A total of 12 036 children were assigned into vaccine group (5 551) and control group (6 485) by cluster sampling. The morbidity of hepatitis A was observed and the blood was collected once hepatitis A showed epidemic to detect anti-HAV IgG and IgM.

During the period of the first 7 months after vaccination, hepatitis A was sporadic, the morbidity of hepatitis A was 0.55/100 000, and only 1 case occurred in the control group and no case in the vaccine group. From January to August 1998, hepatitis A showed epidemic in a township of this county. The morbidities were 0.37% and 6.69% for vaccine group and control group, respectively. The protective efficacy of the vaccine was 94.47%. The ratios of clinical cases to subclinical infections were 1 to 11 and 1 to 1 for vaccine and control groups, respectively (P < 0.05).

The H(2) strain vaccine has a very good protective efficacy, and obviously decreases the attack rate, new infection rate and clinical cases by HAV infection.