Background
The HIV prevalence in Kisumu County, Western Kenya, is more than four times the national average. We estimated HIV incidence in a prospective cohort of adults with multiple sex partners in Kisumu County to identify HIV risk factors and evaluate the feasibility of future HIV vaccine and therapeutic clinical trials.
Methods
We enrolled male and female participants aged 18-35 years who reported sex with at least 2 partners in the preceding 3 months. Visits occurred every 3 months for up to 24 months and included medical history, physical exams, and HIV counseling and testing. Every 6 months, visits included staff-administered questionnaires that collected socio-demographic, general health, and sexual activity information. Demographic and other characteristics ascertained at enrollment were examined for differences between participants who did and did not acquire HIV using Chi-square tests of association. Bivariate Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for factors potentially associated with HIV acquisition over time.
Results
Between January 2017 and August 2021, 619 participants without HIV were enrolled, followed, and analyzed. Of these, 45% were female, 47% aged 25 years and older, 66% single or widowed, and 46% had some secondary education. A total of 11 incident HIV cases occurred over 1117.9 person-years (PY), yielding an incidence rate (IR) of 9.84/1000PY (95%CI: 5.22-17.03). Eight participants acquired HIV during the first year of follow-up (IR: 13.84/1000PY, 95%CI: 6.53-26.11). Unadjusted analyses identified 4+ sexual partners (HR: 4.39, 95%CI: 1.10-17.55), females (HR: 3.44, 95%CI: 0.91-12.98), and forced participation in sexual activity (HR: 9.15, 95%CI:1.17-71.51) as factors associated with HIV seroconversion.
Conclusions
We observed unexpectedly low HIV incidence among sexually active adults in Kisumu, which could be a result of effective HIV prevention programs or possibly the impact of COVID-related behavioral changes. Marginally higher HIV incidence among women may suggest gaps in access and uptake of risk reduction strategies. Diminished HIV risk during the later follow-up period may suggest a beneficial cohort effect from routine engagement and education. These results may inform future efforts to engage people who are vulnerable to HIV but not actively receiving HIV prevention interventions.
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