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

Leidi, A.; Berner, A.; Roxane, D.; Dubos, R.; Koegler, F.; Piumatti, G.; Vuilleumier, N.; Kaiser, L.; Balavoine, J.-F.; Trono, D.; Pittet, D.; Chappuis, F.; Kherad, O.; Courvoisier, D.; Azman, A. S.; Zaballa, M.-E.; Guessous, I.; Stringhini, S.

Objectives: This cohort study including essential workers, assessed the risk and incidence of SARS-CoV-2 infection during the second surge of COVID-19 according to baseline serostatus and occupational sector. Methods: Essential 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. Results: 10457 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. Conclusions: A 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. Keywords: SARS-CoV-2, COVID-19, Reinfection, Essential workers, Occupation