Occupational risk of SARS-CoV-2 infection and reinfection during the second pandemic surge: a cohort study.

ABSTRACT

ObjectivesThis cohort study including essential workers, assessed the{square}risk and incidence of SARS-CoV-2{square}infection during the second surge of COVID-19 according to baseline serostatus and occupational sector. MethodsEssential workers were selected from a seroprevalence survey cohort in Geneva, Switzerland and were linked to a state centralized registry compiling SARS-CoV-2 infections. Primary outcome was the number of virologically-confirmed infections from serological assessment (between May and September 2020) to January 25, 2021, according to baseline antibody status and stratified by three pre-defined occupational groups (occupations requiring sustained physical proximity, involving brief regular contact or others). Secondary outcomes included the incidence of infection. Results10457 essential workers were included (occupations requiring sustained physical proximity accounted for 3057 individuals, those involving regular brief contact, 3645, and 3755 workers were classified under "Other essential occupations"). After a follow-up period of over 27 weeks, 5 (0.6%) seropositive and 830 (8.5%) seronegative individuals had a positive SARS-CoV-2 test, with an incidence rate of 0.2 (95% CI 0.1 to 0.6) and 3.2 (95% CI 2.9 to 3.4) cases per person-week, respectively. Incidences were similar across occupational groups. Seropositive essential workers had a 93% reduction in the hazard (HR of 0.07, 95% CI 0.03 to 0.17) of having a positive test during follow-up with no significant between-occupational group difference. ConclusionsA ten-fold reduction in the hazard of being virologically tested positive was observed among anti-SARS-CoV-2 seropositive essential workers regardless of their sector of occupation, confirming the seroprotective effect of a previous SARS-CoV2 exposure at least six months after infection. Key messagesO_ST_ABSWhat is already known about this subject?C_ST_ABSRisk of SARS-CoV-2 reinfection is low in the general population and among healthcare workers. What are the new findings?A ten-fold reduction of risk of being virologically tested positive reinfection is observed among anti-SARS-CoV-2 seropositive essential workers of different activity sectors, regardless of their occupation-related risk of exposure. How might this impact on policy or clinical practice in the foreseeable future?Vaccination could be delayed in individuals with previous history of SARS-CoV-2 infection with serologic confirmation, regardless of their occupational exposure. These observations need to be confirmed for new SARS-CoV-2 variants.