NEW YORK, Dec 30 (Reuters Health) -- Although the hepatitis B vaccine has been available since 1981, hepatitis B
infection remained as prevalent in the US in the early 1990s as it was in the early 1980s, according to a report in the
January issue of the American Journal of Public Health, a journal of the American Public Health Association.

Dr. Geraldine M. McQuillan and colleagues with the Centers for Disease Control and Prevention (CDC) explain this
finding by the fact that widespread vaccination programs were not launched until the early to mid-1990s. For the last two decades, an estimated 200,000 to 300,000 people in the US have contracted the hepatitis B virus annually. The virus is associated with inflammation of the liver and an increased risk of liver cancer. It can be transmitted via blood
transfusions, sex, and contaminated needles.

The CDC researchers analyzed data from the National Health and Nutrition Examination Survey II (NHANES II), which was conducted between 1976 and 1980, and NHANES III conducted between 1988 and 1994. NHANES II included more than 28,000 people in the US, while NHANES III included an estimated 40,000. The survey design includes the results of blood tests for hepatitis B. The overall prevalence of hepatitis B infection did not change significantly between NHANES II, when it was 5.5%, and NHANES III, when the prevalence was 4.9%, the researchers determined.

In both surveys, the prevalence of hepatitis B was low until age 12, when it increased significantly. In addition,
prevalence was higher than average among those who had multiple sex partners, those who began having sex at an
early age, cocaine users, and men who had sex with men, McQuillan and colleagues report. ``In both surveys and in all racial/ethnic groups, the prevalence of hepatitis B virus infection did not begin to increase until puberty, suggesting that sexual transmission is the primary mode of spread in the United States,'' they explain.

In light of this finding, it is ``not surprising'' that the prevalence of hepatitis B infection did not decline between the early 1980s and the early 1990s, they add. Although a Hepatitis B vaccine was first licensed in the US in 1981, federal
hepatitis B vaccination programs for infants did not begin until late 1992, and programs for adolescents did not start until 1995. Vaccination of healthcare workers and others with work-related risks of infection began in 1981, but did not become widespread until 1991, according to the CDC researchers.

Data from NHANES demonstrate that children have a low but appreciable risk of hepatitis B virus infection that increases significantly at adolescence, presumably with the onset of sexual activity and other high-risk behaviors; this supports the need to routinely vaccinate, McQuillan and co-authors conclude. Future NHANES should provide a means to evaluate the age-specific effect of hepatitis B immunization on infection prevalence.*

(su "VIA", 31 dicembre 1998)