Clinical Research Directory

Inclusion Criteria: Clinical diagnosis of syphilis (primary or secondary) or laboratory-confirmed early latent syphilis. Specifically: This will include persons meeting any one of the following criteria: 1. Clinical diagnosis of primary syphilis (based on the presence of a chancre) and either a positive qualitative RPR in the absence of a prior positive RPR on their most recent serological test for syphilis or a positive darkfield microscope exam of material taken from a chancre, OR 2. Clinical diagnosis of secondary syphilis with a positive qualitative RPR in the absence of a prior positive RPR on their most recent serological test for syphilis, OR 3. A laboratory-confirmed diagnosis of early latent syphilis within one month (i.e. \<31 days prior). Exclusion Criteria: 1. age under 18 2. persons with evidence of neurosyphilis (including ocular and otic syphilis) or tertiary syphilis 3. persons who are unable to give informed consent 4. persons deemed by the study investigators to be unable to complete study follow-up visits 5. persons with an allergy to doxycycline 6. pregnant persons 7. persons with HIV who report that they are off antiretroviral medication or that they are not virologically suppressed 8. persons with other known forms of immunosuppression (e.g., persons taking systemic immunosuppressant drugs, persons with primary immunodeficiencies) 9. persons taking medications that would interact with doxycycline 10. persons whose initial RPR is lower than 1:4 11. persons currently prescribed doxy PEP 12. breastfeeding persons Persons whose initial laboratory serological tests do not confirm the diagnosis of syphilis with an RPR of 1:4 or higher will be informed that they do not meet study criteria and advised to discontinue doxycycline 200mg once daily. Their subsequent treatment will be based on the judgement of non-research, clinical staff in the clinic and reflect shared decision making between clinical providers and their patient.