The prevalence and incidence of HIV-1 infection and syphilis in a cohort of police officers in Dar es Salaam, Tanzania: a potential population for HIV vaccine trials

Objectives: To assess the suitability of a cohort of police officers in Dar es Salaam for HIV vaccine trials by determining the prevalence and inciden ce of HIV-1 infection, active syphilis and their associated factors. Design and setting: An open cohort study of police officers in Dar es Salaa m, Tanzania. Methods: Recruitment of police officers began in 1994. A standardized quest ionnaire was completed at enrolment and subsequent visits. HIV antibodies w ere determined using two consecutive enzyme-linked immunosorbent assays. Sa mples repeatedly discordant on the two tests were tested by a Western blot assay. Treponema pallidum antibodies were first determined by Venereal Dise ase Research Laboratory (VDRL) test and reactive sera were confirmed by Tre ponema pallidum hemagglutination test. Results: At the end of 1996 a total of 2850 police officers had been recrui ted of whom 2733 (96%) consented to be tested for HIV. The overall HIV-1 se roprevalence at recruitment was 13.8% (378 of 2733). Females had a signific antly higher HIV-1 seroprevalence, 18.0% (55 of 306), as compared to males, 13.3% (323 of 2427), P < 0.05. From a total of 2215 married police officer s, 585 (26.4%) responded to a question on extramarital sex within the previ ous 3 months of whom 36.2% (212 of 585) admitted to have had at least one e xtramarital sexual intercourse. Condoms were not used during these encounte rs by 178 of 212 (84.0%). As of 31st December 1998, among the 1524 males ob served for 2553 person-years (PYAR), 50 had seroconverted and among 200 fem ales observed for 357 PYAR, eight had seroconverted. The overall crude HIV- 1 incidence was thus 19.9/1000 PYAR; 19.6 and 22.4/1000 PYAR for males and females, respectively. The overall prevalence and incidence of active syphi lis were 3.1% (88 of 2850) and 8.6/1000 PYAR (26 of 3149), respectively. Ma les had a higher prevalence of active syphilis, 84 of 2525 (3.3%) than fema les, five of 325 (1.5%), P = 0.09. Conclusions: There was high risk sexual practice including low condom use i n this cohort: of police officers. The incidence and prevalence of HIV infe ction were high. Police officers in Dar es Salaam are therefore a potential population group for HIV vaccine evaluation. (C) 2000 Lippincott Williams & Wilkins.