SyphilisSOS GlobalNCT07300254
Treponemal Shedding, Load, and Viability, in Women and Men-who-have-sex-with-women-only With Early Infectious Syphilis: Implications for Transmission
An observational study of Syphilis, run by Monash University at 9 sites in 4 countries.
Trial summary
How syphilis is transmitted between sexual partners is unclear. Asymptomatic detection i.e. detection of syphilis bacteria (Tp) from anatomical sites without lesions, in patients with syphilis infection, suggests that asymptomatic transmission from these sites may play a role. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Syphilis
- How many people
- 480 participants
- Where
- 9 sitesin 4 countries
- Study dates
- 2 Dec 2025to 31 Dec 2028
- Phase
- Observational
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Study population: Women and Men-Who-Have-Sex-With-Women-Only with early infectious syphilis
Who may be able to join
- 1. Any cis-woman, cis-MSW, or nonbinary individuals with a penis who have sex with women only, (who meet all other study criteria) 2. Aged ≥18 years of age, 3. At least one sexual partner in the last 12 months 4. One of either:
- Untreated clinically suspected primary or secondary syphilis. i. Must have rash or lesion(s) clinically suggestive of early infectious syphilis infection.
- May have positive PCR result, positive Dark-ground Microscopy result, positive syphilis serology or positive point-of-care syphilis test, but these are not necessary at the time of enrolment.
- Untreated early latent (no clinical signs indicative of primary or secondary syphilis) syphilis with positive syphilis serology or positive point-of-care test, and one or more of the following(11): i. A documented syphilis seroconversion within the prior 12 months. ii. A sustained (longer than 2 weeks) fourfold or greater increase in the titre in the prior 12 months in a person previously treated for syphilis.
- Unequivocal symptoms of primary or secondary syphilis within the prior 12 months.
- Contact in the prior 12 months with a sex partner who had untreated primary, secondary, or early latent syphilis.
- Documented reactive nontreponemal and treponemal tests, and the only possible exposure occurred during the previous 12 months vi. RPR/VDRL titre >= 1:64 5. Be willing and able to complete study procedures, including physical examination 6. Receiving syphilis treatment on the day of recruitment 7. Have sufficient language proficiency to understand the requirements of the study 8. Provide informed consent as per individual site's local ethics requirements
Who cannot join
- Men, transwomen, or other people, with a penis, who have had any sexual contact, including kissing, oral sex or anal sex, with men (or any other individual with a penis) in the previous one year.
- Individuals who have received antibiotic treatment within 1 month prior to enrolment, with the EXCEPTION of metronidazole.
- Diagnosis of late latent syphilis (>1 year) or latent syphilis of unknown duration.
Trial locations and contacts
9 sites in 4 countries. Contact the study team or a site near you to ask about taking part.
Janet Towns contact
9 sites in 4 countries
United Kingdom4 sites, 3 recruiting
- Recruiting
Burrell Street Clinic, Guy's and St Thomas'
London, SE10UN
Michael Marks, +442076368636, michael.marks@lshtm.ac.uk
- Recruiting
Jefferiss Clinic St Mary's Hospital, Imperial College London
London, W21DL
Michael Marks, +442076368636, Michael.Marks@lshtm.ac.uk
- Recruiting
Mortimer Market Centre
London, WC1E6JB
Michael Marks, +442076368636, michael.marks@lshtm.ac.uk
- Active, not recruiting
London School of Hygiene & Tropical Medicine
London, WC1E7HT
China2 sites, 2 recruiting
- Not yet recruiting
Xinhua Hospital Affiliated to Shanghai Jiaotong University School of Medicine
Shanghai, Shanghai Municipality, 200082
- Not yet recruiting
Shanghai Skin Disease Hospital
Shanghai, Shanghai Municipality, 200443
South Africa2 sites, 2 recruiting
- Not yet recruiting
National Institute for Communicable Diseases
Johannesburg, 2192
- Not yet recruiting
Foundation for Professional Development
Pretoria, 0184
Australia1 site
- Active, not recruiting
Monash University
Melbourne, Victoria, 3004
About this study
Official title: Treponemal Shedding, Load, and Viability, in Women and Men-who-have-sex-with-women Only With Early Infectious Syphilis: Implications for Transmission
How syphilis is transmitted between sexual partners is unclear. Asymptomatic detection i.e. detection of syphilis bacteria (Tp) from anatomical sites without lesions, in patients with syphilis infection, suggests that asymptomatic transmission from these sites may play a role. However, no existing studies have established whether the syphilis bacteria (Tp) detected was viable. This means it is not known if the bacteria at this anatomical site is alive and therefore able to transmit the infection. Further, studies have focused mostly on men who have sex with men, resulting in a lack of evidence regarding anal shedding in men-who-have-sex-with-women only and women (regardless of sexual behaviour), and no data on asymptomatic vaginal shedding in women. This study will explore:
- Patterns of Tp detection in women and men-who-have-sex-with-women only.
- Whether detected Tp from each asymptomatic anatomical sites is viable
- Duration of Tp detection and viability (alive and transmissible bacteria). Patients presenting to a participating sexual health service (overseas only) for management of suspected/confirmed early infectious syphilis will be eligible. During the routine clinical examination, participants will have additional oral and anal swabs, urine, vaginal swab (where relevant), penile skin swab (where relevant) and blood sample collected, in addition to the routine samples taken from the same sites and routine serology collected when syphilis is diagnosed.
- Conditions
- Syphilis
- Being tested
- No Intervention: Observational Cohort
- Keywords
- syphilis, sexual health, syphilis transmission, asymptomatic shedding
- Medical subject headings
- Syphilis
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
No Intervention: Observational CohortOther
No intervention: Observational study
| Study group | Role | What they receive |
|---|---|---|
| Cis-women with suspected or confirmed primary syphilis infection | Cis-women with suspected or confirmed primary syphilis infection Receives: Other: No Intervention: Observational Cohort | |
| Cis-women with suspected or confirmed secondary syphilis infection | Cis-women with suspected or confirmed secondary syphilis infection Receives: Other: No Intervention: Observational Cohort | |
| Cis-women with confirmed early-latent syphilis infection | Cis-women with confirmed early-latent syphilis infection Receives: Other: No Intervention: Observational Cohort | |
| Men-who-have-sex-with-women-only with suspected or confirmed primary syphilis infection | Men-who-have-sex-with-women-only with suspected or confirmed primary syphilis infection Receives: Other: No Intervention: Observational Cohort | |
| Men-who-have-sex-with-women-only with suspected or confirmed secondary syphilis infection | Men-who-have-sex-with-women-only with suspected or confirmed secondary syphilis infection Receives: Other: No Intervention: Observational Cohort | |
| Men-who-have-sex-with-women-only with confirmed early-latent syphilis infection | Men-who-have-sex-with-women-only with confirmed early-latent syphilis infection Receives: Other: No Intervention: Observational Cohort |
What is being measured
The primary outcome is the main question the study is designed to answer.
Number of Biological Samples Testing Positive for Treponema pallidum DNA by PCR
This outcome measures the presence of Treponema pallidum (Tp) DNA in collected biological samples-including lesion swabs, blood, urine, saliva, and oral/anal/genital swabs-using a validated T. pallidum polymerase chain reaction (Tp PCR) assay.
Data will be reported as the number and proportion of samples that test positive, stratified by:
- sample type,
- clinical stage of syphilis,
- anatomical site (where applicable),
- and participant characteristics relevant to the SOS Global protocol. No scale is used; this is a binary laboratory outcome (PCR positive / PCR negative).
Measured: Samples are taken at time of consent - single visit study
Secondary outcomes (2)
Load of Treponema pallidum DNA in Positive Biological Samples by In-house Quantitative PCR (qPCR) assay
This outcome measures the load (copies/mL) of Treponema pallidum (Tp) DNA in collected biological samples-including lesion swabs, blood, urine, saliva, and oral/anal/genital swabs-using an in-house validated quantitative T. pallidum polymerase chain reaction (Tp qPCR) assay.
Data will be reported as a comparison in load between anatomical sites and by clinical stage of syphilis.
Measured: Samples are taken at time of consent - single visit study
Number of Treponema pallidum-Positive Samples Demonstrating Viable Organisms via Novel In-house Viability Assay
This outcome measures the viability of detected Treponema pallidum in PCR-positive biological samples. Viability is assessed using a novel in-house viability assay.
Results will be summarised as the number and proportion of Tp PCR-positive samples that contain viable organisms, stratified by sample type and clinical/epidemiological variables specified in the SOS Global protocol.
This outcome focuses on confirming whether Tp organisms in collected specimens are capable of establishing infection, rather than merely detecting genetic material. The viability assessment does not result in a continuous scale; it is a binary laboratory outcome (viable / non-viable).
Measured: Samples are collected at time of consent - single study visit
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted23 Dec 2025
- Study start2 Dec 2025
- Primary completion30 Jun 2027 (estimated)
- Study completion31 Dec 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for SyphilisStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Observational model
- Case only
- Time perspective
- Cross-sectional
- Enrolment
- 480 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Monash University
- Sponsor type
- University, hospital or other
- Collaborators
- Melbourne Sexual Health Centre, The Alfred
- Responsible party
- Sponsor
- Investigators
- Janet Towns, Principal investigator, Monash UniversityMarcus Chen, Principal investigator, Monash University
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07300254
- Sponsor's protocol ID
- MUCTC-24018
- Acronym
- SOS Global
- Status last verified
- Jan 2026
- First submitted
- 10 Dec 2025
- Last updated
- 3 Apr 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided: Request for data sharing will be considered on a case by case basis
Study at a glance
From the registry record, last updated by the sponsor on 3 Apr 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Treponemal Shedding, Load, and Viability, in Women and Men-who-have-sex-with-women Only With Early Infectious Syphilis: Implications for Transmission
- ClinicalTrials.gov ID
- NCT07300254
- Acronym / sponsor ID
- SOS Global / MUCTC-24018
- Conditions
- Syphilis
- Keywords
- syphilis, sexual health, syphilis transmission, asymptomatic shedding
- Study type
- Observational
- Recruitment status
- Recruiting
- Enrolment
- 480 participants (estimated)
- Lead sponsor
- Monash UniversityUniversity, hospital or other
- Collaborators
- Melbourne Sexual Health Centre, The Alfred
- Study start
- 2 Dec 2025 (actual)
- Primary completion
- 30 Jun 2027 (estimated)
- Study completion
- 31 Dec 2028 (estimated)
- First posted
- 23 Dec 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
How syphilis is transmitted between sexual partners is unclear. Asymptomatic detection i.e. detection of syphilis bacteria (Tp) from anatomical sites without lesions, in patients with syphilis infection, suggests that asymptomatic transmission from these sites may play a role. However, no existing studies have established whether the syphilis bacteria (Tp) detected was viable. This means it is not known if the bacteria at this anatomical site is alive and therefore able to transmit the infection. Further, studies have focused mostly on men who have sex with men, resulting in a lack of evidence regarding anal shedding in men-who-have-sex-with-women only and women (regardless of sexual behaviour), and no data on asymptomatic vaginal shedding in women. This study will explore:
- Patterns of Tp detection in women and men-who-have-sex-with-women only.
- Whether detected Tp from each asymptomatic anatomical sites is viable
- Duration of Tp detection and viability (alive and transmissible bacteria). Patients presenting to a participating sexual health service (overseas only) for management of suspected/confirmed early infectious syphilis will be eligible. During the routine clinical examination, participants will have additional oral and anal swabs, urine, vaginal swab (where relevant), penile skin swab (where relevant) and blood sample collected, in addition to the routine samples taken from the same sites and routine serology collected when syphilis is diagnosed.
Study design
- Observational model
- Case only
- Time perspective
- Cross-sectional
- Number of arms
- 6
| Arm | Type | Receives |
|---|---|---|
| Cis-women with suspected or confirmed primary syphilis infection | – | Other: No Intervention: Observational CohortCis-women with suspected or confirmed primary syphilis infection |
| Cis-women with suspected or confirmed secondary syphilis infection | – | Other: No Intervention: Observational CohortCis-women with suspected or confirmed secondary syphilis infection |
| Cis-women with confirmed early-latent syphilis infection | – | Other: No Intervention: Observational CohortCis-women with confirmed early-latent syphilis infection |
| Men-who-have-sex-with-women-only with suspected or confirmed primary syphilis infection | – | Other: No Intervention: Observational CohortMen-who-have-sex-with-women-only with suspected or confirmed primary syphilis infection |
| Men-who-have-sex-with-women-only with suspected or confirmed secondary syphilis infection | – | Other: No Intervention: Observational CohortMen-who-have-sex-with-women-only with suspected or confirmed secondary syphilis infection |
| Men-who-have-sex-with-women-only with confirmed early-latent syphilis infection | – | Other: No Intervention: Observational CohortMen-who-have-sex-with-women-only with confirmed early-latent syphilis infection |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
- Study population
- Women and Men-Who-Have-Sex-With-Women-Only with early infectious syphilis
Key inclusion criteria (7 listed)
- 1. Any cis-woman, cis-MSW, or nonbinary individuals with a penis who have sex with women only, (who meet all other study criteria) 2. Aged ≥18 years of age, 3. At least one sexual partner in the last 12 months 4. One of either:
- Untreated clinically suspected primary or secondary syphilis. i. Must have rash or lesion(s) clinically suggestive of early infectious syphilis infection.
- May have positive PCR result, positive Dark-ground Microscopy result, positive syphilis serology or positive point-of-care syphilis test, but these are not necessary at the time of enrolment.
- Untreated early latent (no clinical signs indicative of primary or secondary syphilis) syphilis with positive syphilis serology or positive point-of-care test, and one or more of the following(11): i. A documented syphilis seroconversion within the prior 12 months. ii. A sustained (longer than 2 weeks) fourfold or greater increase in the titre in the prior 12 months in a person previously treated for syphilis.
- Unequivocal symptoms of primary or secondary syphilis within the prior 12 months.
Key exclusion criteria (3 listed)
- Men, transwomen, or other people, with a penis, who have had any sexual contact, including kissing, oral sex or anal sex, with men (or any other individual with a penis) in the previous one year.
- Individuals who have received antibiotic treatment within 1 month prior to enrolment, with the EXCEPTION of metronidazole.
- Diagnosis of late latent syphilis (>1 year) or latent syphilis of unknown duration.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| No Intervention: Observational CohortNo intervention: Observational study | Other | Cis-women with confirmed early-latent syphilis infection, Cis-women with suspected or confirmed primary syphilis infection, Cis-women with suspected or confirmed secondary syphilis infection, Men-who-have-sex-with-women-only with confirmed early-latent syphilis infection, Men-who-have-sex-with-women-only with suspected or confirmed primary syphilis infection, Men-who-have-sex-with-women-only with suspected or confirmed secondary syphilis infection |
Primary outcome
Number of Biological Samples Testing Positive for Treponema pallidum DNA by PCR
Time frame: Samples are taken at time of consent - single visit study
This outcome measures the presence of Treponema pallidum (Tp) DNA in collected biological samples-including lesion swabs, blood, urine, saliva, and oral/anal/genital swabs-using a validated T. pallidum polymerase chain reaction (Tp PCR) assay. Data will be reported as the number and proportion of samples that test positive, stratified by: * sample type, * clinical stage of syphilis, * anatomical site (where applicable), * and participant characteristics relevant to the SOS Global protocol. No scale is used; this is a binary laboratory outcome (PCR positive / PCR negative).
2 secondary outcomes
Load of Treponema pallidum DNA in Positive Biological Samples by In-house Quantitative PCR (qPCR) assay
Time frame: Samples are taken at time of consent - single visit study
Number of Treponema pallidum-Positive Samples Demonstrating Viable Organisms via Novel In-house Viability Assay
Time frame: Samples are collected at time of consent - single study visit
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 3 Apr 2026.
- Individual participant dataSharing planned: Undecided. Request for data sharing will be considered on a case by case basis
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Janet Towns contact
Janet Towns principal investigator
Monash University
Marcus Chen principal investigator
Monash University
9 sites in 4 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Syphilis, run by Monash University at 9 sites in 4 countries.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 7 inclusion and 3 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 3 Apr 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 9 sites in United Kingdom, China, South Africa, Australia. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Brigid M Scally (+61399039300, brigid.scally@monash.edu), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Number of Biological Samples Testing Positive for Treponema pallidum DNA by PCR (time frame: Samples are taken at time of consent - single visit study). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 3 Apr 2026.