The Denominator problem: estimating the size of local populations of men-who-have-sex-with-men and rates of HIV and other STIs in Switzerland

Schmidt, Axel J.; Altpeter, Ekkehardt

doi:10.1136/sextrans-2017-053363

Cited by 14 publications

(27 citation statements)

References 20 publications

(21 reference statements)

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“…In our study, however, HIV events were found to occur exclusively in MSM, which raises the additional question whether MSM should be encouraged to transition to PrEP as early as after a first PEP episode. Early transition is also supported by the fact that, compared to HIV incidence rates in the overall MSM population of Zurich (average 2010-2013: 39 per 10,000) 20 , rates retrieved from our study were higher in PEP-seeking MSM (70.5 per 10,000) and in MSM with repetitive PEP seeking (81.1 per 10,000; assuming that all HIV events were captured, and that all participants presumed HIV negative were still at risk at the time of analysis-Supplementary table 1). Although some institutions may have already started considering first PEP-episodes in MSM as an indication for PrEP (as it is currently the case at the USZ), the exact timing of referral to PrEP programs is still lacking in most national and international recommendations 18,21,22 .…”

Section: Discussionmentioning

confidence: 98%

“…Most notably, a series of longitudinal surveys among MSM found that between 2007-2014, PEP uptake ranged between 2.6 and 8% (mean: 5%) 28 . According to a previous report combining several data sources to estimate the size of local MSM populations 20 , the number of MSM in the Zurich area was 16000 (95% credible interval: 14,300-16,500). Combining results on PEP uptake with local MSM population estimates corresponded to an estimated number of 416 to 1280 (mean: 800) PEP prescriptions occurring in Zurich within that timeframe.…”

Section: Discussionmentioning

confidence: 99%

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Data linkage to evaluate the long-term risk of HIV infection in individuals seeking post-exposure prophylaxis

et al. 2021

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Evidence on the long-term risk of HIV infection in individuals taking HIV post-exposure prophylaxis remains limited. In this retrospective data linkage study, we evaluate the occurrence of HIV infection in 975 individuals who sought post-exposure prophylaxis in a tertiary hospital between 2007 and 2013. Using privacy preserving probabilistic linkage, we link these 975 records with two observational databases providing data on HIV events (Zurich Primary HIV Infection study and the Swiss HIV Cohort Study). This enables us to identify 22 HIV infections and to obtain long-term follow-up data, which reveal a median of 4.1 years between consultation for post-exposure prophylaxis and HIV diagnosis. Even though men who have sex with men constitute only 35.8% of those seeking post-exposure prophylaxis, all 22 events occur in this subgroup. These findings should strongly encourage early consideration of pre-exposure prophylaxis in men who have sex with men after a first episode of post-exposure prophylaxis.

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Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Data linkage to evaluate the long-term risk of HIV infection in individuals seeking post-exposure prophylaxis

et al. 2021

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“…Our model population comprised all MSM in Switzerland from 2006 to 2018. We estimated the number of MSM in Switzerland between 2006 and 2018 based on the demographic dynamics of Switzerland by the Federal Statistical Office, Switzerland and Schmidt and Altpeter, 2019[12,13]. In Switzerland, all syphilis cases are anonymously reported to the Federal Office of Public Health (FOPH)[4].…”

Section: Methodsmentioning

confidence: 99%

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

Balakrishna

Salazar‐Vizcaya

Schmidt

et al. 2021

Preprint

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BackgroundOver the last decade, syphilis diagnoses among men-who-have-sex-with-men (MSM) have strongly increased in Europe. Understanding the drivers of the ongoing epidemic may aid to curb transmissions.Methods and FindingsWe set up an epidemiological model to assess the drivers of syphilis in MSM in Switzerland between 2006 and 2017. We stratified the model by syphilis stage, HIV-diagnosis, and behavioral factors to account for syphilis infectiousness and risk for transmission. In the main model, we used ‘reported non-steady partners’ (nsP) as the main proxy for sexual risk. We parameterized the model using data from the Swiss HIV Cohort Study, Swiss Voluntary Counselling and Testing center, cross-sectional surveys among the Swiss MSM population, and published syphilis notifications from the Federal Office of Public Health.The main model reproduced the increase in syphilis diagnoses from 168 cases in 2006 to 418 cases in 2017. It estimated that between 2006 and 2017, MSM with HIV diagnosis had 45.9 times the median syphilis incidence of MSM without HIV diagnosis. Defining risk as condomless anal intercourse with nsP decreased model accuracy (sum of squared weighted residuals, 378.8 vs 148.3). Counterfactual scenarios suggested that increasing screening of MSM without HIV diagnosis and with nsP from once every two-years to twice per year may reduce syphilis incidence (at most 12.8% reduction by 2017). Whereas, increasing screening among MSM with HIV diagnosis and with nsP from once per year to twice per year may substantially reduce syphilis incidence over time (at least 63.5% reduction by 2017).ConclusionsThe model suggests that reporting nsP regardless of condom use is suitable for risk stratification when modelling syphilis transmission. More frequent screening of MSM with HIV diagnosis, particularly those with nsP may aid to curb syphilis transmission.

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“…We define MSM as men who are attracted to other men or who have sex with men, regardless of whether they identify themselves as gay. The population of MSM aged 15–65 in Switzerland (2012) is estimated to be 80 000 (Bayesian 95% credibility interval 64 000 to 96 000) of whom about half live in the five largest cities (Zurich, Geneva, Basel, Lausanne and Bern) 11…”

Section: Methodsmentioning

confidence: 99%

“…Those with undiagnosed HIV infection are among about 20% of MSM in Switzerland who report never having had an HIV test during their life or among the 60% who have not had a test in the last year 10. We estimate that in 2012, 6300 MSM (8%) were living with HIV both diagnosed and undiagnosed, and 1700 (or 2.2%) had non-suppressed HIV infection 11. In addition, an increasing proportion of MSM report condomless anal intercourse with one or more casual sex partners 10…”

Section: Introductionmentioning

confidence: 99%

‘Break the Chains 2015’ community-based HIV prevention campaign for men who have sex with men in Switzerland: non-randomised evaluation and cost analysis

et al. 2020

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ObjectivesTo study the implementation, effects and costs of Break the Chains, a community-based HIV prevention campaign for men who have sex with men (MSM) in Switzerland, from March to May 2015, which aimed to reduce early HIV transmission by promoting the campaign message to adopt short-term risk reduction followed by HIV testing.DesignNon-randomised evaluation and cost analysis.SettingGay venues in 11 of 26 cantons in Switzerland and national online media campaign.ParticipantsMSM in online surveys (precampaign n=834, postcampaign n=688) or attending HIV testing centres (n=885); campaign managers (n=9); and campaign staff (n=38) or further intermediaries (n=80) in an online survey.Primary and secondary outcome measuresThe primary outcome measure was the proportion of MSM at risk of HIV acquisition or transmission who adhered to the campaign message. Secondary outcomes were postcampaign test uptake, knowledge about HIV primary infection and sense of belonging to the gay community.ResultsCampaign staff estimated that they contacted 17 145 MSM in 11 cantons. Among 688 respondents to the postcampaign survey, 311 (45.2%) were categorised as MSM at risk. Of 402/688 (58.5%) MSM who had heard about Break the Chains 2015, MSM categorised as being at risk were less likely to report adherence to the campaign message than MSM not at risk (adjusted OR 0.24; 95% CI 0.14 to 0.42). Twenty per cent of MSM with a defined risk of HIV acquisition or transmission who adopted risk reduction declared having done so because of the campaign. Costs for one MSM at risk to adhere to the campaign message were estimated at USD purchasing power parity 36–55. The number of HIV tests in the month after the campaign was twice the monthly average.ConclusionBreak the Chains increased HIV testing, implying that community-based campaigns are useful HIV prevention strategies for MSM. Additional interventions are needed to reach MSM at the highest risk of infection more effectively.

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The Denominator problem: estimating the size of local populations of men-who-have-sex-with-men and rates of HIV and other STIs in Switzerland

Cited by 14 publications

References 20 publications

Data linkage to evaluate the long-term risk of HIV infection in individuals seeking post-exposure prophylaxis

Data linkage to evaluate the long-term risk of HIV infection in individuals seeking post-exposure prophylaxis

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

‘Break the Chains 2015’ community-based HIV prevention campaign for men who have sex with men in Switzerland: non-randomised evaluation and cost analysis

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