Hepatitis A immunity in the Swedish population. A study of the prevalence of markers in the Swedish population.

After a 20-year interval, the prevalence of seroimmunity to Hepatitis A (HA) was again investigated in a statistical sample of the adult Swedish population. Sera from 3382 of the 4800 originally selected persons were tested. The prevalence of antibodies to HA had not changed since the 1960s when only the Scandinavian population was considered. In the oldest population born at the beginning of this century, the presence of antibodies amounted to 69%. It gradually declined to 6% in those born in the 1940s. In the population born after 1950, the percentage of seropositive individuals was only 2%. A slightly higher prevalence was seen in the big cities, compared with the rural areas (13% vs 9%). Persons of non-Scandinavian origin showed a different pattern. Those from other European countries showed a prevalence of about 70% in all the age-groups investigated. Among the young adults of Arabic or Asiatic origin, the figure was > 90%. The conclusion is that the native Swedish population has a low natural exposure to HA, which has not changed during the last 20 years. Prophylaxis before going to countries where the disease is endemic is strongly recommended.