Epidemiology of hepatitis A before and after the introduction of a universal vaccination programme in Catalonia, Spain.

Summary.  A universal vaccination program for preadolescents, aged 12 years, with the hepatitis A + B vaccine was introduced in 1998 in Catalonia (Spain) with the aim of protecting the whole population against hepatitis A. The hepatitis A + B vaccine program replaced the hepatitis B vaccination program for preadolescent started in 1991. The impact of the hepatitis A + B vaccination program was studied by assessment of the trend of reported cases of hepatitis A. All cases of viral hepatitis reported from 1992 to 2006 were included in the study. To evaluate changes in the epidemiology of hepatitis A, two periods were considered: a prevaccination period (1992–1998) and a post-vaccination period (2001–2006). The ratios of the rates were calculated according to age and sex. The comparison of rates and proportions was made by calculation of the normal z statistic. A total of 7536 cases of viral hepatitis were reported, of which 4109 (54.52%) were hepatitis A. The incidence rate of hepatitis A fell from 5.44 per 100 000 person-years in the prevaccination period to 3.02 in the post-vaccination period. In males, the rate fell from 6.85 to 3.89 and in females from 4.10 to 2.18. The male-female ratio of incidence rates was lower in the post-vaccination period. In males the global decline of incidence rate was 43.26% and in females 46.96%. The greatest decline occurred in the 15 to 19 years age group in both sexes (79.1% in men and 78.34% in women) but declines in the 10–14 years age group were also very important (69.21% and 67.88%, respectively). In conclusion, hepatitis A incidence fell in Catalonia in the post-vaccination period in vaccinated adolescents and also in other unvaccinated groups who have benefited from the indirect effects of the vaccination program.