Persistent efficacy of live attenuated hepatitis A vaccine (H2-strain) after a mass vaccination program.
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 ABBOTT 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.
Zhuang
Fang-cheng
FC
Institute of Viral Diseases, Zhejiang Academy of Medical Sciences, Hangzhou 310013, China. fczhuang@163.com
Qian
Wen
W
Mao
Zi-an
ZA
Gong
Yue-ping
YP
Jiang
Qi
Q
Jiang
Li-min
LM
Chen
Nian-liang
NL
Chai
Shao-ai
SA
Mao
Jiang-sen
JS
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D004797:Enzyme-Linked Immunosorbent Assay; D005500:Follow-Up Studies; D006506:Hepatitis A / Q000517:prevention & control*; D022362:Hepatitis A Vaccines / Q000276:immunology*; D006508:Hepatitis Antibodies / Q000097:blood; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D032541:Mass Vaccination; D014613:Vaccines, Attenuated / Q000276:immunology
D022362:Hepatitis A Vaccines; D006508:Hepatitis Antibodies; D007074:Immunoglobulin G; D014613:Vaccines, Attenuated