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 apopulation for HIV vaccine efficacy trials. The objective of this study wasto estimate the prevalence and incidence of, and determine risk factors forHIV transmission in a rural community-based HIV vaccine preparedness cohortin Masaka, Uganda.

Methods

Between February and July 2004, we conducted a house-to-house HIVsero-prevalence survey among consenting individuals aged 18–60 years.Participants were interviewed, counseled and asked to provide blood for HIVtesting. We then enrolled the HIV uninfected participants in a 2-year HIVsero-incidence study. Medical evaluations, HIV counseling and testing, andsample collection for laboratory analysis were done quarterly. Sexual riskbehaviour data was collected every 6 months.

Results

The HIV point prevalence was 11.2%, and was higher among women thanmen (12.9% vs. 8.6%, P = 0.007). Riskfactors associated with prevalent HIV infection for men were age <25years (aOR = 0.05, 95% CI 0.01–0.35) andreported genital ulcer disease in the past year(aOR = 2.17, 95% CI 1.23–3.83). Amongwomen, being unmarried (aOR = 2.59, 95% CI1.75–3.83) and reported genital ulcer disease in the past year(aOR = 2.40, 95% CI 1.64–3.51) wereassociated with prevalent HIV infection. Twenty-one seroconversions wererecorded over 2025.8 person-years, an annual HIV incidence of 1.04%(95% CI: 0.68–1.59). The only significant risk factor forincident HIV infection was being unmarried (aRR = 3.44,95% CI 1.43–8.28). Cohort retention after 2 years was87%.

Conclusions

We found a high prevalence but low incidence of HIV in this cohort. HIVvaccine efficacy trials in this population may not be feasible due to thelarge sample sizes that would be required. HIV vaccine preparatory effortsin this setting should include identification of higher riskpopulations.