Abstract:
Background: A safe effective and affordable HIV vaccine is the most cost effective way to prevent HIV infection
worldwide. Current studies of HIV prevalence and incidence are needed to determine potentially suitable cohorts
for vaccine studies. The prevalence and incidence of HIV-1 infection among the police in Dar es Salaam in 1996
were 13.8% and 19.6/1000 PYAR respectively. This study aimed at determining the current prevalence and
incidence of HIV in a police cohort 10 years after a similar study was conducted.
Methods: Police officers in Dar es Salaam, Tanzania were prospectively enrolled into the study from 2005 and
followed-up in an incidence study three years later. HIV infection was determined by two sequential enzyme linked
immunosorbent assays (ELISAs) in the prevalence study and discordant results between two ELISAs were resolved
by a Western blot assay. Rapid HIV assays (SD Bioline and Determine) were used for the incidence study.
Results: A total of 1,240 police participated in the HIV prevalence study from August 2005 to November 2008. Of
these, 1101 joined the study from August 2005-September 2007 and an additional 139 were recruited between
October 2007 to November 2008 while conducting the incidence study. A total of 726 (70%) out of the 1043
eligible police participated in the incidence study.
The overall HIV-1 prevalence was 65/1240 (5.2%). Females had a non-statistically significant higher prevalence of HIV
infection compared to males 19/253, (7.5%) vs. 46/987 (4.7%) respectively (p = 0.07). The overall incidence of HIV-1
was 8.4 per 1000 PYAR (95% CI 4.68-14.03), and by gender was 8.8 and 6.9 per 1000 PYAR, among males and
females respectively, (p = 0.82).
Conclusions: The HIV prevalence and incidence among the studied police has declined over the past 10 years, and
therefore this cohort is better suited for phase I/II HIV vaccine studies than for efficacy trials.
