Epidemiology / vaccine efficacy trials. "HIV Incidence in Adults in Northern Thailand".

Unlabelled: According to an abstract submitted by the authors to the X International Conference on AIDS, held August 7-12, 1994, in Yokohama, Japan, "

Objective: To measure the HIV-1 incidence, follow-up rates and high risk behaviors in cohorts of seronegative adults in northern Thailand.

Methods: We screened cohorts of female commercial sex workers (CSWs), male STD clinic patients, Royal Thai Army (RTA) conscripts, and discharged RTA conscripts at baseline and q3 to 6 months for HIV infection by ELISA and WB and did interviews for high risk behavior, medical history, and STD cultures.

Results: Of 1068 CSWs, 409 (38.3%) were HIV positive, and 396 HIV negative were enrolled in the study; follow-up at 6 months was 70.7% and 19 seroconverted, for an incidence of 12.8/100 person years. Of 1031 male STD patients, 164 (15.9%) were HIV positive, and 264 HIV negative (30.4%) were enrolled; follow-up at 6 months was 91.9% and 6 seroconverted, for an incidence of 4.92/100 person years. Of 969 RTA conscripts, 12.4% were HIV positive at baseline and 90% were followed at 6 months; 3 of 778 seroconverted, for an incidence of 0.87/100 person years. (Previous RTA cohorts have had an incidence of 3.4%/year). Among 380 men discharged from RTA, follow-up at 9 months was 81.8% and the incidence was 5.2/100 person years. Sample sizes required to show an HIV vaccine efficacy of 60%, with a power-.90, alpha-.05 varies from CSUs 644, STD patients 1456 to ex-RTA-1306.

Conclusions: Several populations in northern Thailand appear to have sufficiently high HIV-1 incidence and adequate follow-up for HIV vaccine efficacy trials and other preventive intervention trials.