The first study of doxycycline postexposure prophylaxis for cisgender women did not reduce incident STIs likely due to low use of doxycycline. Researchers will conduct a pilot study of once-weekly doxyxycline to prevent bacterial STIs among Kenyan cisgender women using PrEP for HIV prevention.

A study evaluating doxycycline prophylaxis to prevent sexually transmitted infections (STIs) in PrEP-taking African women, who are a priority population for STI prevention, given their high risk and engagement in longitudinal prevention services. The primary study objective is to assess the acceptability of once weekly doxycycline prophylaxis and assess persistence in once weekly doxycycline delivered as directly observed therapy (DOT). STI prophylaxis carries substantial potential benefits but also important potential risks, and we have framed our work as capturing key data to inform this question. Researchers hypothesize that weekly doxycycline will substantially reduce the incidence of curable STIs, particularly C. trachomatis, the most common bacterial STI and the one responsible for greatest morbidity.

Researchers' secondary study objectives are to evaluate the impact on incidence rate of STIs in women given once-weekly doxycycline DOT in comparison with data collected among participants assigned to received standard of care in recently completed dPEP Kenya study as well as to assess tolerability of once weekly doxycycline prophylaxis. Researchers will collect samples for future doxycycline hair drug level testing, antibiotic resistance testing, and microbiome evaluation.

Inclusion Criteria:

1. Willing and able to give written informed consent
2. Age 18-30 years
3. Female sex assigned at birth
4. HIV-seronegative, according to national HIV testing algorithm
5. Has a current prescription for PrEP, > 1 month, according to the national guidelines of Kenya

Exclusion Criteria:

1. Pregnant
2. Breastfeeding a child
3. Allergy to tetracycline class
4. Current medications which may impact doxycycline metabolism or that are contraindicated with doxycycline, as per the prescribing information. These include systemic retinoids, barbiturates, carbamazepine, phenytoin, and warfarin.
5. Active, clinically significant medical or psychiatric conditions that would interfere with study participation, at the discretion of the site investigator or designee.
6. Prior enrollment in The dPEP Kenya Study

cis-gender women

Adverse Events collected from enrollment up to 6 months post-enrollment.