Cohort Profile: Prospective Cohort to Study the COVID-19 Immune Response in Retail Workers in Quebec, Canada (CISACOV)

Retail workers are an understudied occupational group that may have been at increased risk of contracting SARS-CoV-2 during the COVID-19 pandemic. To explore this question, we set up a longitudinal cohort of participants working in this sector to document the rate of SARS-CoV-2 infection and the immune response to infection and/or vaccination. A total of 304 participants were recruited between April 20th, 2021 and October 22nd, 2021. They were invited to attend three visits (each separated by [~]12 weeks) during which they provided blood samples. Information was collected on participant characteristics, SARS-CoV-2 detection tests done, COVID-19 symptoms, and vaccination. An extension phase of two additional visits was carried out between March 15th, 2022 and October 3rd, 2022 to document the impact of the Omicron variant among the 198 participants who were still eligible for recruitment. Participants were aged 18 to 75 and worked in grocery stores, hardware stores, bars or restaurants within the Quebec City metropolitan area (Canada). Findings to date: This article describes participants demographic, socioeconomic, behavioral, occupational and clinical characteristics, and their COVID-19 symptoms (when applicable), as well as SARS-CoV-2 vaccination status and any SARS-CoV-2 positive diagnostic test (i.e., PCR or rapid antigen) from the beginning of the pandemic until the last visit. The goals of this study were: to assess the rate of SARS-CoV-2 infection, and the immune response (innate and acquired) to SARS-CoV-2 infection or vaccination using a variety of techniques. The humoral immune response was measured by reference and experimental enzyme-linked immunosorbent assays, as well as microneutralization assays with live viruses and experimental pseudoneutralization with an angiotensin-converting enzyme 2-spike assay. Cellular immune response was evaluated by using the viral analog R848 to activate peripheral blood mononuclear cells and neutrophils.