Objective: To characterize associations between exposures within and outside the medical workplace with healthcare personnel (HCP) SARS-CoV-2 infection, including the effect of various forms of respiratory protection.
Design: Case-control study.
Setting: Data collected via online survey from international participants.
Participants: 1130 HCP (244 cases with laboratory-confirmed COVID-19, 886 controls healthy throughout the pandemic) from 67 countries not meeting pre-specified exclusion (healthy but not working, missing workplace exposure data, COVID symptoms without lab confirmation).
Methods: Respondents were queried regarding workplace exposures, respiratory protection, and extra-occupational activities. Odds ratios for HCP infection were calculated with multivariable logistic regression and sensitivity analyses controlling for confounders and known biases.
Results: HCP infection was associated with non-aerosol-generating contact with COVID-19 patients (adjusted OR 1.4, 95% CI 1.04-1.9, p=0.03) and extra-occupational exposures including gatherings of ten or more, patronizing restaurants or bars, and public transportation (adjusted ORs ranging 3.1-16.2). Respirator use during aerosol-generating procedures (AGPs) was associated with lower odds of HCP infection (adjusted OR 0.4, 0.2 to 0.8, p=0.005), as was exposure to intensive care and dedicated COVID units, negative pressure rooms, and personal protective equipment (PPE) observers (adjusted ORs ranging 0.4-0.7).
Conclusions: COVID-19 transmission to HCP was associated with medical exposures currently considered lower-risk and multiple extra-occupational exposures, while exposures associated with proper use of appropriate PPE were protective. Closer scrutiny of infection control measures surrounding healthcare activities and medical settings considered lower risk, and continued awareness of the risks of public congregation, may reduce the incidence of HCP infection.