WHEN IS HELICOBACTER-PYLORI INFECTION ACQUIRED

Cross sectional surveys have shown an increasing prevalence of Helicob acter pylori (H pylori) infection with increasing age in Western popul ations. The aim of this study was to examine the pattern of acquisitio n of H pylori infection over a 21 year period in a group of 141 adults who had blood samples and serum stored in 1969, 1978, and 1990. A pre valence of H pylori antibody of 39% in 1969 serum samples, 40.9% in 19 78, and 34.8% in 1990 was found when assessed by an enzyme linked immu nosorbent assay (ELISA). Of the 86 subjects who were seronegative in 1 969, only six (7%) were seropositive in 1990. These data suggest that a cohort effect may contribute to the pattern of increasing prevalence of H pylori infection seen with increasing age. Acquisition of infect ion in adults is rare. It is unlikely, therefore, that reinfection wil l occur after successful eradication.