Persistent efficacy of live attenuated hepatitis A vaccine （H2-strain） after a mass vaccination program

• Published in: Chinese medical journal Vol. 118; no. 22; pp. 1851 - 1856
• Main Author: ZHUANG Fang-cheng QIAN Wen MAO Zi-an GONG Yue-ping JIANG Qi JIANG Li-min CHEN Nian-liang CHAI Shao-ai MAO Jiang-sen
• Format: Journal Article
• Language: English
• Published: 2005
• Subjects: 免疫机制; 甲型肝炎; 疫苗接种; 血液检查
• ISSN: 0366-6999; 2542-5641

Background Live attenuated hepatitis A vaccine （ H2 strain） is widely applied in prevention of hepatitis A epidemic in China and other countries now. It is essential to observe and confirm the vaccine immune efficacy, population antibody level and its persistent efficacy after mass immunization. Methods A total of 220 children with negative anti-HAV antibody （ aged 1-3 years） were taken for follow-up assay to observe seroconversion and geometric mean titre（GMT） level 2 months, 12 months, 6 years, and 10 years after inoculation. Another survey sampled from subjects of different age groups （3, 6, 9, 15, 18, 25 and 35 years） to compare anti-HA antibody positive rate before and after inoculation performed 10 years previously. Epidemiological observations were taken for 10 years to evaluate the relationship between vaccine coverage and hepatitis A morbidity. Serum antibody to HAV was detected by enzyme linked immunoassay （ELISA, calibrated by WHO international reference） and ABBOTY Axsym HAVAB microparticle enzyme immunoassay. Results Seroconversion in follow-up assay 2 months and 10 years after inoculation was 98.6% and 80. 2% respectively. For children, the vaccination anti-HA antibody positive rates were significantly different before and after 10 years, 7.69% cf 70.45% （aged 3 years） and 52. 58% cf 71.78% （aged 18 years）. When vaccine coverage rose from 57% to 74%, there were no any HA epidemics. When vaccine coverage reached 85%, there were no any HA cases. With vaccine coverage between 85% and 91%, there were no any HA cases in cohorts from the age of 1 year to 15 years during the 10 years. Conclusions Live attenuated hepatitis A vaccine has an obvious long-term effectiveness in prevention and control of HA epidemics through mass vaccination.