Monday, June 3, 2019

TIME-TO-EVENT ANALYSIS OF EFFECTIVENESS OF HIV POST-EXPOSURE PROPHYLAXIS IN A NAIROBI SEX WORKERS COHORT


Research Project by Jane Musimbi Evelia
W62/88856/2016
University of Nairobi

ABSTRACT
Background: The current overall HIV prevalence in Kenya is 4.8%, yet research on effectiveness of non-occupational Post-Exposure Prophylaxis (PEP) for HIV prevention is still patchy and consequent risks poorly understood.
Objective: To characterize the PEP real-world effectiveness and prospective sexual health risks among.
Methods: Data from sex workers aged ≥18 years prescribed PEP as from 2016 to 15th October 2018 were analyzed. A comparison group of non-PEP/non-Pre-Exposure Prophylaxis (PrEP) enrolled as from 2016 was used and random sample of 503 taken for comparative analysis in a ratio of 1:1. Socio - demographic comparison of profiles was done at baseline using a Chi-squared test. Kaplan-Meier cumulative event and hazard functions and Cox proportional hazards models were fitted, in analyses that included PrEP, for time-to-ARV initiation. Results: There were 42.9% of 196 PEP users and 57.1% (comparison group) whose data were linked with baseline data. Chi-square test for differences resulted in statistical significance in age categories (p=0.0027) and in sex work duration (p<0.001) between the PEP and the Comparison group. There were 8 (0.64%) total HIV infections (ARV initiations), 6 (1.3%) from the Control group and 2 (0.64%) from Pre-Exposure Prophylaxis (PrEP) group. Five (3.1%) incident HIV-infection/ARV initiation among MSMW and 3 (0.28%) among FSW found. Men who have sex with men (MSMW) were at higher risk of HIV compared to female sex workers (FSW) with hazard ratio of 17.2 (p<0.00001). In total 52 (9.35%) sex workers had repeat PEP prescriptions with 90.3%, 8.4%, 1.1% and 0.2% having had 1,2,3 and 4 PEP episodes respectively. PEP recurrence rate was 8.6 per 100 person-months of follow up. There was HIV event-free survival in the PEP group. Univariable and multivariable Cox models yielded same results. Multiple pairwise log-rank test indicated presence of significant survival difference between PEP and Controls (p-value=0.046), insignificant differences between PEP and PrEP (p=0.025) and PrEP and Control group (p=0.631) and evidence of clinically significant results. Survival among PEP users was comparative better hence effective but not statistically significant at alpha 0.05.
Conclusions: There is evidence that PEP is effective when adherently taken and associated with event-free survival but this is not statistically significant. The underpin the potential need to scale up condom counseling and in formulating personalized risk scores for treatment as HIV prevention among the sex workers for behavioural risk change and more focus on MSM.

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