Aims: To assess the level of immunity in a healthy population to the hepatitis A virus (HAV), according to age groups and in an urban health area.
Design: Transversal random prospective study of a sample of the population found by letters. SITE. Primary Care Centre covering the population of an urban health area in Valladolid.
Patients or other participants: Random sample of 726 people with an adjustment as to sex and age according to the area's average, in line with the full census of the above area. The sample was 95% trustworthy, with a 3% margin of error. People with serious illness at the time of the study were excluded.
Measurements and main findings: We carried out a social-health count. We established the anti-HAV titer after its detection by enzyme immunoanalysis (HAVAB EIA Abbott); the titers were inferred from the absorbances relating then to that of a a "pool" of serums with very high titers. 69.9% (standardised rate) gave positive. The highest titers were presented in people between 31 and 50 (29.7 +/- 47.0), with significant differences both for lower (17.0 +/- 15.7) and higher (15.7 +/- 19.8) age groups (p. 0.001 for both).
Conclusions: The highest anti-HAV titers corresponded to people in the middle age-group, with a subsequent dropping-off. This could suggest a greater susceptibility to HAV infection in the older person.