To determine whether horizontal transmission of the hepatitis B virus contributes to the high prevalence of infection with this virus in an endemic region, residents of five villages in Zambia were tested for hepatitis B serologic markers. The prevalence of hepatitis B was determined by testing samples from 620 residents. By examining paired serum samples from 79 children and 80 adults, it was determined that new infections occurred during the five years of this study in at least 14 children (18%) (aged 4-17 years) and ten adults (12%) (aged 23-65 years). These 24 new infections were distributed among 20 households and were not associated with active HBV infections in the mother or, in most cases, other family members. Intervention to prevent hepatitis B in regions such as rural Zambia will require vaccination of susceptible children and adults as well as newborn infants.
One hundred and one of 255 recipients of a plasma-derived hepatitis B vaccine were evaluated in 1990, 9 years after the first vaccine dose in a study in Zambia to evaluate the efficacy of one, two, or three doses. In 1983, 2 years after the first vaccine dose, antibody to the hepatitis B surface antigen (anti-HBs) had been detectable in 90 of these 101 participants (89%). In 1990, anti-HBs was still detectable in 72 of 101 (71%), and was present at a protective level (> or = 10 mIU/mL) in 68 of 101 (67%). Although the original vaccine study elicited a protective level of antibody in a greater percentage of children and adolescents than in adults, there were no significant differences among the three groups at 9 years. (In 1990, anti-HBs was still detectable in 52 of 70 [74%] who had had no serologic markers of the hepatitis B virus in 1981, and a protective level was detected in 47 of 70 [67%].) A protective level of anti-HBs was detected in 1990 in 26 of 36 (72%) recipients of three doses and in 23 of 31 (74%) recipients of two doses; the slightly lower prevalence among recipients of one dose (19 of 34 [56%]) was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)
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