PREVALENCE, INCIDENCE, AND PROGRESSION OF HUMAN IMMUNODEFICIENCY VIRUS INFECTION IN HOMOSEXUAL AND BISEXUAL MEN IN HEPATITIS B VACCINE TRIALS, 1978–1988

Between 1978 and 1980,359 hepatitis B seronegative homosexual and bisexual men were recruited from the San Francisco municipal sexually transmitted disease clinic for hepatitis B vaccine trials. Of the 359 participants, 320 (89%) consented to have their stored blood samples tested for human immunodeficiency virus antibodies. The prevalence of human immunodeficiency virus infection in these 320 vaccine trial participants rose from 0.3% in 1978 to 50.9% in 1988. The annual incidence of human immunodeficiency virus infection showed that seroconversion peaked in 1980-1982, dropped significantly in 1983, and has remained low. Men < 30 years old on entry into the study seroconverted earlier in the epidemic and had higher incidence rates than men 30 years or older (p = 0.07). No statistical difference in seroconversion rates was found for other demographic variables. Using a Kaplan-Meier survival curve of the cumulative proportion of men without acquired immunodeficiency syndrome by duration of human immunodeficiency virus infection, an estimated 39% (95% confidence interval 27%–51%) will develop acquired immunodeficiency syndrome within 9.2 years of infection. Cox proportional hazard stepwise analysis showed no correlation between age at seroconversion, race, or year of seroconversion and progression to acquired immunodeficiency syndrome.