Assessing the drivers of syphilis among men who have sex with men in Switzerland reveals a key impact of screening frequency: A modelling study

Impact of screening and doxycycline prevention on the syphilis epidemic among men who have sex with men in British Columbia: a mathematical modelling study

Background

Men who have sex with men (MSM) in British Columbia (BC) are disproportionately affected by infectious syphilis and HIV. In this study, we developed a co-interaction model and evaluated the impact and effectiveness of possible interventions among different MSM subgroups on the syphilis epidemic.

Methods

We designed a deterministic compartmental model, which stratified MSM by HIV status and HIV pre-exposure prophylaxis (HIV-PrEP) usage into (1) HIV-negative/unaware MSM (HIV-PrEP not recommended, not on HIV-PrEP), (2) HIV-negative/unaware MSM with HIV-PrEP recommended (not on HIV-PrEP), (3) HIV-negative/unaware MSM actively on HIV-PrEP, and (4) MSM diagnosed with HIV. We estimated the effect of scaling up syphilis testing frequency from Status Quo to six-, four-, and three-months, increasing the percentage of MSM using doxycycline prevention (Doxy-P) to 25%, 50%, and 100% of the target level, and a combination of both among subgroups (2)-(4). We also assessed the impact of these interventions on the syphilis incidence rates from 2020 to 2034 in comparison to the Status Quo scenario where no intervention was introduced.

Findings

Under the Status Quo scenario, with the expansion of the HIV-PrEP program to improve syphilis testing, the syphilis incidence rate was estimated to peak at 16.1 [Credible Interval (CI):14.2-17.9] per 1,000 person-years (PYs) in 2023 and decrease to 6.7 (CI:3.8-10.9) per 1,000 PYs by 2034. The syphilis incidence rate in 2034 was estimated at 0.7 (0.3-1.3) per 1,000 PYs if MSM diagnosed with HIV could be tested every four months, and at 1.5 (0.7-3.0) per 1,000 PYs if HIV-negative/unaware MSM actively on HIV-PrEP could be tested every three months. By achieving 100% of the target coverage of Doxy-P, the syphilis incidence rate was estimated at 1.4 (0.5-3.4) if focusing on MSM diagnosed with HIV, and 2.6 (1.2-5.1) per 1,000 PYs if focusing on HIV-negative/unaware MSM actively on HIV-PrEP. Under the combined interventions, the syphilis incidence rate could be as low as 0.0 (0.0-0.1) and 0.8 (0.3-1.8) per 1,000 PYs, respectively.

Interpretation

The HIV-PrEP program in BC plays a crucial role in increasing syphilis testing frequency among high-risk MSM and reducing syphilis transmission among this group. In addition, introducing Doxy-P can be an effective complementary strategy to minimize syphilis incidence, especially among MSM diagnosed with HIV.

Funding

This work was funded by the Canadian Institutes of Health Research.

Position statement of the German STI Society on the prophylactic use of doxycycline to prevent STIs (Doxy-PEP, Doxy-PrEP)

Over the past two decades, there has been a rise in the incidence of syphilis, particularly among men who have sex with men (MSM). This has sparked interest in studying the prophylactic use of doxycycline to prevent syphilis and other sexually transmitted infections (STIs), commonly referred to as Doxycycline Pre- or Post-Exposure Prophylaxis (Doxy-PrEP, Doxy-PEP). At the same time, demand from potential users for this preventive measure is increasing. Several randomized controlled trials have demonstrated that the prophylactic use of doxycycline in MSM and trans women using HIV pre-exposure prophylaxis (HIV-PrEP) or living with an HIV infection effectively reduces the risk of syphilis and chlamydia infections. At present, however, unresolved questions remain, particularly regarding implications of a broad implementation of prophylactic doxycycline to prevent STIs on tetracycline and other antimicrobial resistance in bacterial STIs, non-STI-related bacterial pathogens, and the microbiome. In response to the increasing demand and the challenge of balancing effectiveness, safety, and the risk of promoting antibiotic resistance, the German STI Society (DSTIG) has issued a position statement, providing specific recommendations regarding potential indications, criteria, and occasions for the use of doxycycline in STI prevention. These recommendations are based on current evidence and expert opinion.

Stellungnahme der Deutschen STI-Gesellschaft zur antibiotischen STI-Prophylaxe mit Doxycyclin (Doxy-PEP, Doxy-PrEP): Position Statement of the German STI Society on the Prophylactic Use of Doxycycline to Prevent STIs (Doxy-PEP, Doxy-PrEP)

Seit etwa zwei Jahrzehnten ist eine Zunahme der Syphilisinzidenz zu beobachten, insbesondere unter Männern, die Sex mit Männern haben (MSM). Diese Entwicklung hat zu einem wachsenden Interesse an Studien zur prophylaktischen Anwendung des Antibiotikums Doxycyclin zur Vermeidung von Syphilisinfektionen und anderen sexuell übertragbaren Infektionen (STI), international meist als Doxycyclin‐Prä‐ beziehungsweise Post‐Expositionsprophylaxe (Doxy‐PrEP, Doxy‐PEP) bezeichnet, geführt. Zugleich steigt die Nachfrage seitens potenzieller Nutzer nach dieser präventiven Maßnahme.

Mehrere randomisierte kontrollierte Studien haben gezeigt, dass die prophylaktische Anwendung von Doxycyclin bei MSM und Trans‐Frauen mit HIV‐PrEP‐Gebrauch oder bekannter HIV‐Infektion das Risiko einer Syphilis‐ und Chlamydien‐Infektion wirksam reduziert. Zum gegenwärtigen Zeitpunkt bestehen jedoch noch offene Fragen, insbesondere hinsichtlich der möglichen Auswirkungen einer breiten Anwendung der antibiotischen STI‐Prophylaxe mit Doxycyclin auf Tetrazyklin‐ und andere antimikrobielle Resistenzen bei bakteriellen STI, anderen bakteriellen Pathogenen und Bakterien des Mikrobioms.

Angesichts der steigenden Nachfrage und der Herausforderung, eine Abwägung zwischen Wirksamkeit, Sicherheit und dem Risiko der Förderung von Antibiotikaresistenzen vorzunehmen, hat die Deutsche STI‐Gesellschaft (DSTIG) die vorliegende Stellungnahme erarbeitet. Diese enthält spezifische Empfehlungen zu potenziellen Indikationen, Kriterien und Anlässen für den Einsatz von Doxycyclin zur Prävention von STI. Die Empfehlungen basieren auf aktuellen Studienergebnissen und der Meinung von Fachpersonen.

Persistently Elevated Risk of Syphilis Among Human Immunodeficiency Virus-Positive Men Receiving Care in a Status-Neutral Setting: A Retrospective Analysis

BACKGROUND

Over the past decade, the incidence of primary and secondary syphilis has increased dramatically in the United States and Western Europe. Men living with human immunodeficiency virus (HIV) and those at risk of HIV infection experience disproportionately high rates of early syphilis (ES). We compared the odds of ES among HIV-positive and HIV-negative men participating in a status-neutral comprehensive HIV prevention and treatment program (CHP).

METHODS

We conducted a retrospective analysis of men aged 18 to 65 years with ≥ 1 CHP visit and ≥2 rapid plasma reagin (RPR) tests performed between January 1, 2018, and December 31, 2021. Early syphilis was defined as newly reactive RPR with a minimum titer of ≥1:4 or a ≥ 4-fold increase in the RPR titer. Multiple logistic regression analyses were performed to determine predictors of ES.

RESULTS

A total of 2490 men met the inclusion criteria, of whom 1426 (57.3%) were HIV-positive and 1064 (42.7%) were HIV-negative. Of the 393 men with ES, 284 (72.3%) were HIV-positive and 109 (27.7%) were HIV-negative. Human immunodeficiency virus-positive men had higher adjusted odds of ES (adjusted odds ratio, 2.86; 95% confidence interval, 2.45-3.27) than HIV-negative men did. Chlamydia or gonorrhea infection did not differ according to HIV status (adjusted odds ratio, 0.93; 95% confidence interval, 0.82-1.04).

CONCLUSIONS

In our status-neutral care setting, HIV-positive status was associated with significantly higher odds of ES, but not chlamydia or gonorrhea. Our findings emphasize the vulnerability of HIV-positive men to syphilis in an era of effective HIV biomedical prevention.

Triggers of Change in Sexual Behavior Among People With HIV: The Swiss U U Statement and COVID-19 Compared

We assessed changes in sexual behavior among people with human immunodeficiency virus (HIV) over 20 years. Condom use with stable partners steadily declined from over 90 to 29 since the Swiss U U statement, with similar trajectories between men who have sex with men (MSM) and heterosexuals. Occasional partnership remained higher among MSM compared to heterosexuals even during coronavirus disease 2019 (COVID-19) social distancing.

Risk Factors and Incidence of Sexually Transmitted Infections in the Swiss HIV Cohort Study

Background

Sexually transmitted infections (STIs) are common among people with human immunodeficiency virus (PWH), but there are limited data about risk factors and incidence of STIs in large, representative cohort studies.

Methods

We assessed incidence and risk factors of STIs reported by treating physicians within the Swiss HIV Cohort Study (SHCS). Sexually transmitted infections and demographic, clinical, and behavioral characteristics were prospectively collected at 6-month follow-up visits between October 2017 and November 2019. We used multilevel Poisson regression to assess incidence rate ratios of different STIs.

Results

Among 10 140 study participants, a total of 1634 STIs in 1029 SHCS participants were reported over 17 766 person-years of follow up (PYFUP). The overall incidence of any reported STI was 91.9 per 1000 PYFU (95% confidence interval [CI], 85.8 -98.5). Among the 1634 STI episodes, there were 573 (35.1%) incident cases of syphilis, 497 gonorrhea (30.4%), and 418 chlamydia (25.6%). Men who have sex with men (MSM) younger than 50 years represented 21% of the study population, but accounted for 61% of reported STIs. Male sex (adjusted incidence rate ratio [aIRR], 2.03; 95% CI, 1.36-3.02), MSM (aIRR, 3.62; 95% CI, 2.88-4.55), age group 18-34 years (aIRR, 1.78; 95% CI, 1.51-2.10), history of sexual relationships with occasional partners (aIRR, 6.87; 95% CI, 5.40-8.73), and reporting injecting drug use (aIRR, 2.48; 95% CI, 1.91-3.23) were associated with a higher risk of incident STIs.

Conclusions

Sexually transmitted infections were frequent among PWH and varied considerably between age and risk groups. Screening programs and recommendations for STI testing need to be adapted according to risk factors and demographic characteristics.

Social and behavioural determinants of syphilis: Modelling based on repeated cross-sectional surveys from 2010 and 2017 among 278,256 men who have sex with men in 31 European countries

Background

Syphilis case notifications among men-who-have-sex-with-men (MSM) have increased markedly over the past two decades in Europe. We tested several potential factors for this resurgence.

Methods

Self-reported data from two cross-sectional waves of the European MSM Internet Survey (EMIS-2010 and EMIS-2017, N = 278,256 participants living in 31 European countries) were used to fit multivariable hierarchical logistic regression models designed to evaluate potential social, behavioural, and interventional determinants of syphilis diagnosis. Additional multivariable hierarchical negative binomial models investigated determinants of the number of non-steady male condomless anal intercourse (CAI) partners. We tested the hypothesis that more CAI and syphilis-screening are associated with syphilis resurgence, both linked to use of pre-exposure prophylaxis (PrEP).

Findings

Between 2010 and 2017, incidence of syphilis diagnosis in the previous 12 months rose from 2.33% (95%CI: 2.26–2.40) of respondents reporting a syphilis diagnosis in 2010 compared with 4.54% (95%CI: 4.42–4.66) in 2017. Major factors contributing to syphilis diagnosis were living with diagnosed HIV (adjusted odds ratio (aOR) 2.67, 95%CI: 2.32–3.07), each additional non-steady male CAI partner (aOR 1.01, 95%CI: 1.01–1.01), recency of STI-screening (previous month vs no screening, aOR 25.76, 95%CI: 18.23–36.41), selling sex (aOR 1.45, 95%CI: 1.27–1.65), and PrEP use (aOR 3.02, 95%CI: 2.30–3.96). Living with diagnosed HIV (adjusted incidence rate ratio (aIRR) 3.91, 95%CI: 3.77–4.05), selling sex (aIRR 4.39, 95%CI: 4.19–4.59), and PrEP use (aIRR 5.82, 95%CI: 5.29–6.41) were associated with a higher number of non-steady male CAI partners. The association between PrEP use and increased chance of syphilis diagnosis was mediated by STI-screening recency and number of non-steady male CAI partners, both substantially higher in 2017 compared to 2010.

Interpretation

Syphilis cases are concentrated in three MSM population groups: HIV-diagnosed, PrEP users, and sex workers. Behavioural and interventional changes, particularly more non-steady male CAI partners and recency of STI-screening, are major contributing factors for increasing syphilis diagnoses among MSM in Europe.

Funding

European Centre for Disease Prevention and Control.