Sexual behaviours among MSM during the first COVID-19 lockdown not associated with risk of COVID-19 infection

Abstract Background: The social distancing measures associated with the COVID-19 pandemic had far reaching effects on sexual behavior worldwide. However, it remains unclear whether sexual contact with non-steady partners was a contributor to the spread of SARS-CoV-2. The aim of this study was to (i) assess whether the SARS-CoV-2 seropositivity after the first pandemic wave among people using HIV Pre-Exposure Prophylaxis (PrEP) in Zurich, Switzerland differed from that of a demographic matched population level comparison group, (ii) describe risk factors for SARS-CoV-2 seropositivity in this population, and (iii) determine whether sexual contact with non-steady partners was associated with SARS-CoV-2 seropositivity. Methods: The study was conducted between July 2020 and October 2020 as a nested cross-sectional study within two ongoing cohort studies, SwissPrEPared (all eligible PrEP users in Switzerland ≥18 years old) and Corona Immunitas (a series of cross-sectional and longitudinal studies measuring the SARS-CoV-2 seroprevalence across Switzerland, beginning in April 2020). All SwissPrEPared participants were recruited from Checkpoint Zurich (the main PrEP clinic in Zurich). Data were collected on participants’ SARS-CoV-2 antibody status, social characteristics and behavioral data after the first wave of the corona pandemic in Switzerland, and seroprevalence was compared with a propensity score-matched sample from the general Zurich population. Results: Of the 218 participants enrolled, 8.7% (n=19, 95% CI: 5.5-13.5%) were seropositive for SARS-CoV-2 during the first pandemic wave, higher than that of the general male population in Zurich aged 20-65 (5.5%, 95% CI: 3.8–8.2%). Participants on average reduced their social outings, but the seronegative were more socially active before, during, and after the first lockdown period. In a logistic model, increasing mean sexual partner count was not associated with seropositivity (OR: 0.9, 95% CI: 0.8, 1.0), but increasing number of trips abroad was associated with higher seropositivity (p=0.06, OR: 1.14, 95% CI: 1.0, 1.3). The estimated risk ratio for seropositivity for the participants compared to the general Zurich population after propensity score matching was 1.5 (95% CI: 0.53, 4.0). 94% of participants reported later receiving a COVID-19 vaccination. Discussion: Our study suggests that COVID-19 seropositivity was slightly elevated among people taking PrEP in Zurich during the first wave of the pandemic, but that socializing and sexual activity were less important than other factors in contributing to risk.