NCT06738407 · Westat
Doxycycline Prophylaxis for Prevention of Sexually Transmitted Infections
What this study is about
The goal of this where both patients and doctors know the treatment given, randomly assigned trial is to assess the effectiveness of doxycycline prophylaxis in reducing incidences of bacterial sexually transmitted infections (STIs) among adolescent and young adult females while also evaluating acceptability and antimicrobial resistance in order to inform public health policy.
View original scientific description
The goal of this open-label, randomized trial is to assess the efficacy of doxycycline prophylaxis in reducing incidences of bacterial sexually transmitted infections (STIs) among adolescent and young adult females while also evaluating acceptability and antimicrobial resistance in order to inform public health policy.
Interventions
DRUG
Doxycycline hyclate delayed released 200 mg
200 mg of doxycycline taken by mouth as soon as possible and within 72 hours after any condomless oral, vaginal, and/or anal sex along with STI screening and sexual health counseling
DRUG
Doxycycline hyclate delayed released 200 mg weekly
200 mg of doxycycline taken by mouth weekly regardless of sexual activity along with STI screening and sexual health counseling
OTHER
Per standard of care with quarterly STI testing/treatment and sexual health counseling
Quarterly STI testing/treatment and sexual health counseling
Primary outcome measures
Combined incidence of GC, CT, and/or early syphilis infection
Time frame: One (1) year
Overall combined incidence of GC, CT, and/or early syphilis infection by laboratory-based diagnosis (defined as positive GC or CT on nucleic acid amplification test \[NAAT\] or first positive rapid plasma reagin \[RPR\] with positive treponemal-specific antibody \[Ab\] or a new 4-fold rise in RPR titers) over the duration of follow-up.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- Age 13-29 years, inclusive;
- Self-reports GC, CT, and/or early syphilis diagnosis in the 12 months prior to screening;
- Self-reports condomless (oral, vaginal, and/or anal) intercourse at least once in the 30 days prior to screening
- Is at least 45 kilograms (99.2 pounds) in weight
- Fluent in English (able to read, speak, and understand English);
- Willing to undergo all required study procedures; and
- Willing to provide written informed consent to participate in the study.
Exclusion criteria
- Is pregnant, breastfeeding, or planning to become pregnant in the next 12 months;
- Documented history of tetracycline allergy or self-reports an allergy to tetracyclines;
- Current or anticipated use of a medication (e.g., barbiturates, phenytoin, lithium, carbamazepine, systemic retinoids, warfarin) with a contraindicated interaction to doxycycline ;
- Current or planned use of doxycycline for a prolonged period (\> 2 weeks) in the 30 days prior to enrollment, including current prescription for doxycycline for STI prophylaxis;
- Prolonged antibiotic use (\> 2 weeks) within the last 30 days prior to enrollment;
- Co-enrollment in any other concurrent interventional research or studies that may interfere with this study, such as an STI prevention trial, unless approved by Protocol Team in writing;
- Does not have consistent access (or anticipated weekly access for 52 weeks of survey completion) to smartphone that can access the HMP app; or
- Any other medical condition, medical/behavioral intervention, or other conditions that, in the opinion of the clinical site Project Lead (PL)/Investigator of Record (IoR) or designee, could interfere with adherence to study procedures or compromise interpretation of study results.
Where
- Los Angeles, California
- San Francisco, California
- Washington D.C., District of Columbia
- Tampa, Florida
- Atlanta, Georgia
- Chicago, Illinois
- New Orleans, Louisiana
- Baltimore, Maryland
- New York, New York
- Chapel Hill, North Carolina
- Philadelphia, Pennsylvania
- Memphis, Tennessee
And 1 more location — see the full list below.
Collaborators
Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institute of Allergy and Infectious Diseases (NIAID), National Institute on Drug Abuse (NIDA), National Institute of Mental Health (NIMH), Florida State University, The Office of the Director, National Institutes of Health (NIH)
Related conditions & keywords
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced May 15, 2026 · Source of record for eligibility and locations