LAUSR

Background Understanding the factors influencing SARS-CoV-2 transmission in asylum seekers and refugees living in centres is crucial to determine targeted public health policies protecting these populations. We explored the pandemic's spread into asylum centres during the first wave of the pandemic (May-June 2020) in Switzerland and factors associated with the presence of SARS-CoV-2 antibodies. Methods This research is part of SerocoVID, a seroepidemiologic study of SARS-CoV-2 infection conducted in Canton of Vaud, Switzerland. All migrants living in two asylum centres were invited to participate. Anti-Spike IgG and IgA antibodies were measured in all participants. Each participant completed a questionnaire measuring socio-demographic characteristics, medical history, health literacy, public health recommendations, behaviours and exposures. The association of independent variables with serologic test result were estimated using a multivariable logistic regression model. Results The mean (SD) age of the 124 participants (23% women) was 33.7 (11.6) years (Centre 1, n = 82;Centre 2, n = 42). The mean participation rate was 37%. The seroprevalence in Centres 1 and 2 were 13% [95% CI 3-14%] and 50 [34-65%], respectively. Next, 41% of SARS-CoV-2 positive people never developed symptoms, and no one had developed severe Covid-19 disease. After adjusting for individual characteristics and centre, seropositivity was higher among people with low health literacy (aOR 6.2, p = 0.010 [1.6, 24.8]) and non-smokers (aOR 5.4, p = 0.013 [1.4- 20.3]). No other significant associations were found. Conclusions Findings suggest that developing targeted public health measures, especially for low health literacy people, would be necessary to limit the risk of outbreaks in asylum centres and improve this population's safety. Further investigations are required to understand better the negative association between tobacco consumption and SARS-CoV-2 infection. Key messages Asylum centres require specific public health measures to guarantee their population's safety and limit the virus spread. Asylum seekers and refugees with low health literacy seem particularly vulnerable during the Covid-19 pandemic.