Background:
Doxycycline postexposure prophylaxis taken following a condomless sexual exposure reduces incident bacterial STIs among men who have sex with men but not among cisgender women in initial trials. Adherence is a key component of effective biomedical interventions, and some initial trials of HIV PrEP among cisgender women reported null results due to low adherence, especially among those under 24 years old, despite having increased risk of HIV acquisition. Lack of efficacy reported in the dPEP Kenya Study were likely due to low use of doxycycline; factors associated with use have not yet been reported.
Methods:
We conducted an analysis of doxycycline use among all follow-up visits of a randomly selected subset (n=50; 200 person-visits) of participants assigned to doxycycline PEP (doxycycline hyclate 200mg taken within 72 hours of sex) within an open-label randomized trial among 449 women aged 18-30 years in Kisumu, Kenya. Participants returned quarterly over one year for STI testing and behavioral surveys; and provided hair samples for objective detection of doxycycline. The 1cm hair segment from the scalp, representing exposure over approximately the preceding month, was tested for doxycycline detectability (>0.020 ng/mg) using liquid chromatography-tandem mass spectrometry. Baseline and time-varying covariates potentially associated with doxycycline detection were assessed using modified Poisson regression with robust standard errors and generalized estimation equations.
Results:
Doxycycline was detected in 29.0% (58/200) of hair samples, 32.6% (58/178) when censoring pregnancy time off doxycycline. Age of 24 years or older, an independent income source, more than one partner, and no primary sex partner were all associated with detection of doxycycline. After adjustment, older age and not having a primary partner both remain significantly associated with exposure (Table). Common risk factors for STI exposure, e.g., higher frequency of sex, transactional sex, or prior STI, were not associated with detection of doxycycline (Table). Participants reporting concern about getting an STI 34.4% (22/64) or concern that primary partner had other partners 29.1% (23/79) did not exhibit an increase in doxycycline detection.
Conclusions:
Among young cisgender women taking HIV PrEP with a high prevalence and incidence of STIs, the use of doxycycline for STI prevention was overall low. Detection of doxycycline using objective measures was associated with older age and not having a primary sex partner.
