甲型肝炎减毒活疫苗（H2株）10年流行病学效果观察

目的：观察在甲型肝炎（甲肝）高发县、区用甲肝减毒活疫苗（H2株）大面积接种后长期的流行病学保护效果。方法：选择浙江省嵊泗县和椒江区二个试点，二组小学生定群研究，观察4年。试点内1－15岁儿童普遍接种甲肝活疫苗，部分研究对象作血清中和试验。免疫回忆反应及免后10年抗体检测。结果：接种组与未接种组甲肝发病率判别具有显著性（P＜0．01），疫苗保护率为100％。疫苗接种率与甲肝发病率二者具有明显负相关，全人口甲肝发病率分别下降了94．5％和90．3％，1－15岁儿童组发病专率分别下降了96．9％和97．9％，10年期间没有发生甲肝流行血清学检测结果：免后阴性血清，用体外中和法验证有63．8％仍有中和作用，加强免疫1针后回忆反应明显。免后10年抗－HAV－IgG的阳性率为80．2％，结论：甲肝减毒活疫苗（H2株）长期的流行病学效果明显。通过普遍接种甲肝活疫苗，第一次在甲肝高发地区和高发年龄组消除了甲肝的发生与流行。

Epidemiological effects of live attenuated hepatitis Avaccine(H2-strain):results of A 10-year observation

OBJECTIVE: To assess the long-term epidemiological effects after a mass vaccination program, using live attenuated hepatitis A vaccine (H(2)-strain). METHODS: Shengsi county and Jiaojiang city in Zhejiang province were chosen where high incidence rate of hepatitis A was observed. Mass vaccination program of H(2)-strain vaccine was carried out on 1 - 15 year olds. Cohort studies included two groups were carried out in Shengsi. Cases reported program on hepatitis A was under the national standard on clinical diagnosis and partly through laboratory monitor of anti-HAV IgM and IgG, ELISA and Abbott EIA. Population size was estimated by the yearly reports of census bureau of the county and the city. Serum tests including neutralization test, immune-recall responses, and anti-HAV IgG were performed 10 years after the initial immunization. RESULTS: The morbidity of hepatitis A was significantly different between vaccinated groups and non-vaccinated groups (P < 0.01) in the cohort study. The protective efficacy in the site was 100 percent. There was a significantly negative correlation of regression between vaccine coverage and hepatitis A morbidity. In both sites, hepatitis A incidence rate showed decrease of 94.5% and 90.3% in whole population, with 96.9% and 97.9% in 1 - 15 year olds respectively. Neutralization test showed that 63.8% of the serum negative to ELISA after vaccination could still neutralize certain HAV. Immune-recall response after the booster was seen in vaccine group with 80.2% positive rate of anti HAV-IgG, 10 years after immunization among vaccinees in both sites. Not a single hepatitis A case was identified. CONCLUSION: Live attenuated hepatitis A vaccine seemed to have obviously long-term epidemiological effects.