Screening and evaluation of potential volunteers for a phase III trial in Thailand of a candidate preventive HIV vaccine (RV148) ★

Screening for the community-based, phase III, prime-boost HIV vaccine trial conducted in Thailand (also referred to as “RV144”) began in September 2003 and concluded in December 2005 in Rayong and Chon Buri provinces. During this period 26,676 persons were consented and screened for vaccine trial eligibility in a separate protocol (“RV148”) at 47 screening sites, of which 26,548 were tested for HIV, and 16,402 were ultimately enrolled in RV144 and received at least one vaccination or corresponding placebo injection. Fifty-eight percent of those enrolled in RV148 were men and roughly half of the men and women were married. A slight majority was born in the provinces in which the study was conducted. The median age was 23 (IQR 20–26) and most had achieved a level of education that was higher than grade 9, which is compulsory for Thai citizens. The prevalence of confirmed HIV infection was 1.6%; among persons who did not return for confirmatory testing, it was 2.0%. Eighty-three percent were infected with CRF01_AE strains (formerly subtype E) as determined by serological typing. The estimated incidence of HIV infection using a capture EIA assay was 0.19 per 100 person-years. Female sex, older age, single marital status, and lower educational attainment were associated with HIV infection. Persons who reported working in the fishing or sex-work industries were more frequently infected (2.4% and 4.1%, respectively), but accounted for a small percent of the tested population in RV148 (0.7% and 0.6%, respectively), reflecting the overall low-risk of HIV in this study. Those screened for eligibility but did not participate in the vaccine trial were not substantially different from enrolled vaccine trial subjects.