title: [Long-term immunogenicity and effectiveness of live attenuated hepatitis A vaccine (H2-strain)-a study on the result of 15 years' follow up].
abstract: OBJECTIVE
  To evaluate the long-term immunogenicity and effectiveness of live attenuated hepatitis A (HA) vaccine (H2 strain) after one dose injection, through a 15 years' follow up observation.
  
  
  METHODS
  A total of 220 children with negative anti-HAV antibody (aged 1-3 y) were involved and followed up in Jiaojiang district, Taizhou city, Zhejiang province. Indicators would include seroconversion and geometric mean titer (GMT) levels after inoculation the vaccine with single dose at 2 m, 12 m, 6 years, 10 years and 15 years. Epidemiological observation was carried out within the 15 years to evaluate the relationship between vaccine coverage, the incidence of HA and the overall effectiveness. In the studied population, serum was tested by ELISA (calibrated by WHO international reference) and ABBOTT Axsym HAVAB mEIA.
  
  
  RESULTS
  Seroconversion rates were found to be 98.6% and 81.3% after 2 months and 15 years of inoculation and slowly decreased. GMT level was 128 mIU/ml after 15 years, significantly higher than the required protective level of 20 mIU/ml, recommended by WHO experts. Effectiveness through the 15-year follow up program showed a significant correlation between vaccine coverage and incidence of HA in 1-15 years aged group (Kendall-Rank test, τ =-0.931, P<0.01). There was no HA case seen among the observed accumulated 236 413 person-year vaccines, compared to 4 HA cases discovered in the 27 206 person-year of the non-vaccinees. The overall protective rate reached 100%. Through a mass vaccination program on children, the whole population established an immune-defence to enable the incidence of HA decreased by 96.7%.
  
  
  CONCLUSIONS
  The long-term immunogenicity and effectiveness of live attenuated hepatitis A vaccine (H2 strain) after one dose injection could last as long as 15 years.
authors.affiliation: Institute of Viral Disease, Zhejiang Academy of Medical Sciences, Hangzhou 310013, China. fczhuang@163.com
authors.forename: Fang-cheng
authors.initials: FC
authors.lastname: Zhuang
authors.forename: Zi-an
authors.initials: ZA
authors.lastname: Mao
authors.forename: Li-min
authors.initials: LM
authors.lastname: Jiang
authors.forename: Jie
authors.initials: J
authors.lastname: Wu
authors.forename: Yue-qing
authors.initials: YQ
authors.lastname: Chen
authors.forename: Qi
authors.initials: Q
authors.lastname: Jiang
authors.forename: Nian-liang
authors.initials: NL
authors.lastname: Chen
authors.forename: Shao-ai
authors.initials: SA
authors.lastname: Chai
authors.forename: Jiang-sen
authors.initials: JS
authors.lastname: Mao
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D005260:Female; D006506:Hepatitis A / Q000453:epidemiology / Q000276:immunology* / Q000517:prevention & control*; D022362:Hepatitis A Vaccines / Q000276:immunology; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D032541:Mass Vaccination; D014613:Vaccines, Attenuated / Q000276:immunology
chemical_list: D022362:Hepatitis A Vaccines; D014613:Vaccines, Attenuated