Nine-year follow-up study of a plasma-derived hepatitis B vaccine in a rural African setting.

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)