甲型肝炎减毒活疫苗免疫原性与保护效果的研究

目的 观察国产甲型肝炎（甲肝）减毒活疫苗（H2株与LA－1株）的免疫原性及预防效果。方法 在广西、河北、上海等地457251例观察对象中进行随机对照试验,比较接种疫苗组与对照组甲肝发病率,观察轩保护效果;并筛选易感者,观察疫苗接种后发生甲肝感染的转归及免疫后甲肝抗体阳性率与持久性。结果 H2株（10^7.0TCID50）与LA－1株（10^6.75TCID50)疫苗保护效果均达95％,抗体阳转率峰值分别出现在疫苗接种后2个月与6个月,为94.9%与86.0%,3年后抗体阳性率下降至75％－80％,但保护效果不变。结论 国产甲肝减毒活疫苗（H2株与LA－1株）具有很好免疫原性与保护效果,可与国外灭活疫苗相媲美。接种者可通过隐性感染获得加强免疫。

Immunogenicity and efficacy of two live attenuated hepatitis A vaccines (H(2) strains and LA-1 strains)

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.