Occupational risk of infection and reinfection by SARS-CoV-2 during the second pandemic wave

Leidi A, Berner A, Dumont R, Dubos R, Koegler F, Piumatti G, Vuilleumier N, Kaiser L, Balavoine JF, Trono D, Pittet D, Chappuis F, Kherad O, Courvoisier DS, Azman AS, Zaballa ME, Guessous I, Stringhini S, SEROCoV-WORK+ study group.
Occupational risk of SARS-CoV- 2 infection and reinfection during the second pandemic surge: a cohort study.Occupational and Environmental Medicine 2021;0:1-4. doi:10.1136/oemed-2021-107924

Abstract

Objectives: This cohort study including essential workers assessed the risk of SARS-CoV- 2 infection during the second wave of COVID-19 according to their initial serological status and their occupational sector.

Methods Essential workers were selected from participants in a seroprevalence survey in Geneva (Switzerland) that took place between May and September 2020. The variable of interest was the incidence of virologically confirmed infections (PCR or antigenic test) between the serological test and 25 January 2021, according to initial serological status and stratified by three occupational groups (occupations requiring prolonged physical proximity, involving brief regular contact or other).

Results 10,457 essential workers were included (3,057 in occupations requiring prolonged physical proximity, 3,645 in occupations involving brief contact. Finally, 3755 workers were classified as "other essential occupations"). After a follow-up of more than 27 weeks, 5 (0.6%) seropositive and 830 (8.5%) seronegative workers tested positive for SARS-CoV-2, 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 in all occupational groups. The study showed a 93% reduction in the risk of obtaining a positive test (HR of 0.07, 95% CI 0.03 to 0.17) for HIV-positive workers, with no difference observed between occupational groups.

Conclusions A 10-fold reduction in the risk of retesting positive for SARS-COV-2 was observed among essential seropositive workers regardless of their occupational exposure, confirming the protective effect of a previous SARS-COV-2 infection at least 6 months after infection.

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