[Seroepidemiology of hepatitis A in six departments in West-Central France in 1991].

Antibodies to hepatitis A virus were sought for among residents of 6 "départements" of West-Central France during a routine medical check up provided by the national health insurance system to all affiliated persons. Among them 5,641 subjects (aged 6 to 60) were randomly selected to a sample size of 256 +/- 15 male or female subjects for each five-year age group. Anti-HAV were detected in 51% of the screened population. The prevalence was less than 5% in the 6-15 age group and increased by successive steps to exceed 90% in the subjects over 50. The highest increase was observed between the 26-30 (39%) and the 31-35 (57%) age groups. This study confirms the influence of socio-economical factors on the anti-HAV prevalence rate. Factors such as profession or scholar education were previously known, but the housing conditions and especially the number of siblings were identified in our present report. In relation to this low prevalence of anti-HAV among young adults, one may fear an increase of overt hepatitis cases which are known to be more frequent in adults than in infants or children. Moreover any break in hygiene may expose the population to an epidemia. Only active immunization with a vaccine against hepatitis A could efficiently prevent these individual and community-related risks.