Hong Kong is a well developed city in the center of an endemic region for h
epatitis A. The age at which hepatitis A occurs has shifted from childhood
and adolescence to adults like many western countries. There is a high chan
ce of outbreaks with the introduction of infection from neighbouring countr
ies. Reducing the susceptibility of a population by vaccination can elimina
te the diseases but updated sero-epidemiological data is needed to analyse
the level of natural immunity, and identify those susceptible to infection
for preventive measures. This study conducted amongst secondary school chil
dren seeks to identify those who are at risk and to obtain data on the pres
ent sero-prevalence of anti-HAV. Overall prevalence of anti-HAV in this a p
e group was 7% increasing with age. Analysed by multiple regression model,
those students living in mainland China over 3 years had odds ratio of 31.6
(95% c.i. 17.4-57.3) compared with those born in Hong Kong. Students with
a father in a skilled occupation and an education level of secondary school
or above, and both parents with secondary education or above, had an odds
ratio of 0.22 (95% c.i. 0.07-0.7) and 0.35 (95% c.i. 0.17-0.72) associated
with presence of anti-HAV, respectively. Improved socio-economic state expo
ses higher proportion of the population at risk. Immunisation is worthwhile
to be considered for the adolescents in Hong Kong. Prevaccination screenin
g is cost effective only for those adolescents who are most likely to have
natural immunity. (C) 1999 Elsevier Science Ltd. All rights reserved.