The Kenya Medical Research Institute (KEMRI) Wellcome Trust Research Programme (KWTRP) maintains an ongoing cohort study of men who have sex with men (MSM) and female sex workers in Coastal Kenya. In MSM, overall HIV-1 incidence has been estimated as 6.9 (95% CI: 5.7-8.5) per 100 person years observation, and several studies documented risk factors for HIV-1 and sexually transmitted infection (STI) acquisition. Despite risk reduction counselling, provision of water-based lubricants and condoms, treatment of STI, and provision of hepatitis B vaccinations, HIV-1 incidence has not declined in MSM over the past 12 years. In May 2017, Kenya became the second country in Africa, after South Africa, to launch a national PrEP roll out through the National AIDS & STI Control Programme, making PrEP available to individuals meeting HIV-1 risk criteria in the published guidelines. Wahome’s study will assess if PrEP offered programmatically to MSM and FSW in the cohort will lead to reductions in the high HIV-1 incidence in MSM and FSW. In order to guide PrEP targeting for MSM, she developed an empiric risk score based on four risk behaviours including having sex with men exclusively, receptive anal intercourse, unprotected sex, and group sex. Through this risk score, she will assess the uptake of, and adherence to PrEP in a cohort of approximately 200 MSM in follow up in Mtwapa, and estimate reductions of HIV-1 incidence in MSM on and off PrEP. Modelling studies have suggested that consistent use of PrEP may reduce the risk of HIV-1 infection by up to 99%, however, there are public health concerns that individuals on PrEP may have increased rates of STIs compared to those not on PrEP. In addition, Wahome will assess the incidence of chlamydia and or gonorrhea in MSM on and off PrEP. It is important to understand if MSM on PrEP will have reduced HIV-1 incidences and increased risks of STIs. Her studies may help understand the effectiveness of PrEP in reducing HIV-1 acquisition which will impact the design of a future HIV-1 vaccine trial.