Effects of HIV Oral Pre-Exposure Prophylaxis Use on Incidence of STIs and Risky Sexual Behaviors among Female Sex Workers at the Drop-In Centers in Nairobi County, Kenya

Abstract

Pre-exposure Prophylaxis (PrEP) is effective in prevention of Human Immunodeficiency Virus (HIV) infections among populations at a substantial risk. Approximately 39 million HIV related mortalities have been recorded to date and over 2 million people contract HIV annually, while HIV rate among FSWs estimated to be about 12% globally. World Health Organization (WHO) recommended use of PrEP for HIV prevention in 2012 and by 2020, over 930,000 people worldwide had been initiated on PrEP. However, risk compensation among Female Sex Workers (FSWs) raises concerns about increased risk of sexually transmitted Infections (STIs). While STIs screening is continually done at every PrEP refill visits and cases treated, increased risk of STIs may reduce the prevention benefits of PrEP while increasing STI rates with ultimate impact on economic and health burdens. This study investigated the effects of HIV oral PrEP on the incidences of STIs and risky sexual behaviors among female sex workers in Nairobi. A six months retrospective cohort study was conducted among FSWs comprising of both HIV oral PrEP users and non-PrEP users accessing services at selected Drop-in Centers (DICEs) in Nairobi County. Multi stage sampling was employed to select Sub Counties, DICEs and participants, to generate a sample size of 168 PrEP users and 168 non-PrEP users. A structured data abstraction tool was used to collect the desired data on STI incidences, condom use and average sexual acts. This data was abstracted from the participant records as documented during monthly routine data collection. Data was analyzed using STATA. Oral PrEP users were found to be 1.8 times at increased risk of STIs (P=0.005, 95%CI) than non-PrEP users. Vaginitis (62%) and cervicitis (21%) were the most common STIs identified among FSWs with a composite STI prevalence of 35.4% and pooled STI incidence rate of 14 per 1000 person years. The average number of sexual acts per day was significantly higher among oral PrEP users than non-PrEP users from month two to month six with a 1.0-unit increase in mean sexual acts among PrEP users (P=.004, 95%CI). PrEP users were at increased risk of STIs than non-PrEP users with hazard ratio of 1.82 (P=.005, 95%CI) and relative risk (RR) of 1.4 (P=.012, 95%CI). There was no significant difference in mean condom use between PrEP users and non-users from month one to month five, but a statistically significant difference in mean condom use at month six, 4.3 and 5.0 PrEP and non-PrEP use respectively (P=0.05, 95%CI). There was a 0.38 mean reduction in condom use among PrEP users, but statistically insignificant (P=.179, 95%CI). This study has demonstrated that: Vaginitis, cervicitis and Pelvic Inflammatory Disease (PID) are the most prevalent STIs among FSWs; PrEP use among FSWs increases likelihood of higher daily sexual acts suggestive of behavioral risk compensation; Use of oral PrEP for HIV prevention increases the risk of STIs among FSWs using oral PrEP; and PrEP use does not influence condom use among FSWs. Prevention counseling should be emphasized during PrEP initiation and throughout PrEP follow up visits