Seroprevalence and Risk Factors for Severe Acute Respiratory Syndrome Coronavirus 2 Among Incarcerated Adult Men in Quebec, Canada, 2021.

Background: People in prison are at increased risk of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We examined the seroprevalence of SARS-CoV-2 and associated carceral risk factors among incarcerated adult men in Quebec, Canada.

Methods: We conducted a cross-sectional seroprevalence study in 2021 across 3 provincial prisons, representing 45% of Quebec's incarcerated male provincial population. The primary outcome was SARS-CoV-2 antibody seropositivity (Roche Elecsys serology test). Participants completed self-administered questionnaires on sociodemographic, clinical, and carceral characteristics. The association of carceral variables with SARS-CoV-2 seropositivity was examined using Poisson regression models with robust standard errors. Crude and adjusted prevalence ratios (aPR) with 95% confidence intervals (95% CIs) were calculated.

Results: Between 19 January 2021 and 15 September 2021, 246 of 1100 (22%) recruited individuals tested positive across 3 prisons (range, 15%-27%). Seropositivity increased with time spent in prison since March 2020 (aPR, 2.17; 95% CI, 1.53-3.07 for "all" vs "little time"), employment during incarceration (aPR, 1.64; 95% CI, 1.28-2.11 vs not), shared meal consumption during incarceration ("with cellmates": aPR, 1.46; 95% CI, 1.08-1.97 vs "alone"; "with sector": aPR, 1.34; 95% CI, 1.03-1.74 vs "alone"), and incarceration post-prison outbreak (aPR, 2.32; 95% CI, 1.69-3.18 vs "pre-outbreak").

Conclusions: The seroprevalence of SARS-CoV-2 among incarcerated individuals was high and varied among prisons. Several carceral factors were associated with seropositivity, underscoring the importance of decarceration and occupational safety measures, individual meal consumption, and enhanced infection prevention and control measures including vaccination during incarceration.