Objective: To assess the efficacy and immunogenicity of two live attenuated hepatitis A vaccines.
Methods: Randomized and controlled clinical trials were conducted in Guanxi, Hebei and Shanghai, 457 251 children were enrolled. The efficacy for preventing clinical hepatitis A was calculated by the comparison of incidence rate of disease between vaccine group and control group. Susceptible subjects tested anti-HAV negative before the study were followed up after vaccination for determination of the immunogenicity and vaccine efficacy to prevent subclinical infection.
Results: The protective efficacy to prevent clinical infection by both H(2) and LA-1 vaccines were 95%. The peak of seroconversion was observed in 94.9% and 86.0% respectively for the two vaccines. The seroconversion rate decreased to 75% approximately 80% in the third year, but the vaccine protection against clinical hepatitis A has remained unchanged throughout the 3 years.
Conclusion: Both strains of the live attenuated hepatitis A vaccines have good immunogenicity and high protection against clinical disease, the efficacy to prevent subclinical infection is not significant. The subclinical HAV infection serves as a natural booster for the vaccinees.