Seroprevalence and risk factors of exposure to COVID-19 in homeless people in Paris, France: a cross-sectional study

Background During the COVID-19 lockdown period from March 17 to May 11, 2020, French authorities in Paris and its suburbs relocated people experiencing recurrent homelessness to emergency shelters, hotels, and large venues. A serological survey was done at some of these locations to assess the COVID-19 exposure prevalence in this group. Methods We did a cross-sectional seroprevalence study at food distribution sites, emergency shelters, and workers' residences that were provided medical services by Medecins Sans Frontieres in Paris and Seine-Saint-Denis in the Ile-de-France region. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody seropositivity was detected by Luciferase-Linked Immunosorbent Assay and Pseudo Neutralization Test. Sociodemographic and exposure related information was collected via a verbal questionnaire to analyse risk factors and associations with various COVID-19 symptoms. Findings Between June 23 and July 2, 2020, 426 (52%) of 818 individuals recruited tested positive in 14 sites. Seroprevalence varied significantly by type of recruitment site (chi(2) p<0.0001), being highest among those living in workers' residences (88.7%, 95% CI 81.8-93.2), followed by emergency shelters (50.5%, 46.3-54.7), and food distribution sites (27.8%, 20.8-35.7). More than two thirds of COVID-19 seropositive individuals (68%, 95% CI 64.2-72.2; 291 of 426) did not report any symptoms during the recall period. COVID-19 seropositivity was strongly associated with overcrowding (medium density: adjusted odds ratio [aOR] 2.7, 95% CI 1.5-5.1, p=0.0020; high density: aOR 3.4, 1.7-6.9, p<0.0001). Interpretation These results show high exposure to SARS-CoV-2 with important variations between those at different study sites. Living in crowded conditions was the strongest factor associated with exposure level. This study underscores the importance of providing safe, uncrowded accommodation, alongside adequate testing and public health information. Copyright (C) 2021 The Author(s). Published by Elsevier Ltd.

Automated summary

Between June 23 and July 2, 2020, a seroprevalence study conducted at 14 sites in Paris and Seine-Saint-Denis in the Ile-de-France region found that 52% of the 818 individuals recruited tested positive for COVID-19 antibodies. Seroprevalences varied significantly by type of recruitment site, with the highest in workers' residences (88.7%), followed by emergency shelters (50.5%), and food distribution sites (27.8%). Over two thirds of COVID-19 seropositive individuals did not report any symptoms during the recall period, and living in crowded conditions was strongly associated with exposure level.