Prevalence and Incidence of HIV in a Rural Community-Based HIV Vaccine Preparedness Cohort in Masaka, Uganda

BACKGROUND Local HIV epidemiology data are critical in determining the suitability of a population for HIV vaccine efficacy trials. The objective of this study was to estimate the prevalence and incidence of, and determine risk factors for HIV transmission in a rural community-based HIV vaccine preparedness cohort in Masaka, Uganda. METHODS Between February and July 2004, we conducted a house-to-house HIV sero-prevalence survey among consenting individuals aged 18-60 years. Participants were interviewed, counseled and asked to provide blood for HIV testing. We then enrolled the HIV uninfected participants in a 2-year HIV sero-incidence study. Medical evaluations, HIV counseling and testing, and sample collection for laboratory analysis were done quarterly. Sexual risk behaviour data was collected every 6 months. RESULTS The HIV point prevalence was 11.2%, and was higher among women than men (12.9% vs. 8.6%, P = 0.007). Risk factors associated with prevalent HIV infection for men were age <25 years (aOR = 0.05, 95% CI 0.01-0.35) and reported genital ulcer disease in the past year (aOR = 2.17, 95% CI 1.23-3.83). Among women, being unmarried (aOR = 2.59, 95% CI 1.75-3.83) and reported genital ulcer disease in the past year (aOR = 2.40, 95% CI 1.64-3.51) were associated with prevalent HIV infection. Twenty-one seroconversions were recorded over 2025.8 person-years, an annual HIV incidence of 1.04% (95% CI: 0.68-1.59). The only significant risk factor for incident HIV infection was being unmarried (aRR = 3.44, 95% CI 1.43-8.28). Cohort retention after 2 years was 87%. CONCLUSIONS We found a high prevalence but low incidence of HIV in this cohort. HIV vaccine efficacy trials in this population may not be feasible due to the large sample sizes that would be required. HIV vaccine preparatory efforts in this setting should include identification of higher risk populations.