Health workers were at higher risk for SARS-CoV-2 infection during the COVID-19 pandemic due to occupational risk factors. As part of the WHO Unity Studies initiative, we aimed to characterise these risk factors.
This global, multicentre, nested, case-control study was conducted in 121 healthcare facilities in 21 countries. Cases were health workers who tested positive for SARS-CoV-2 infection with a documented occupational exposure to COVID-19 patients in the 14 days pre-enrolment. Controls were enrolled from the same facility with a similar exposure but negative serology. Case and control status was confirmed with serological testing at baseline and after 3-4 weeks. Demographic and infection risk factor data were collected using structured questionnaires.
Between June 2020 and December 2021, data were obtained for 1213 cases and 1844 controls. SARS-CoV-2 infection risk was associated with non-adherence to personal protective equipment (PPE) guidelines (aOR 1·67 [95% CI 1·32-2·12]) and not consistently performing hand hygiene after patient contact (aOR 2·52 [1·72-3·68]). Direct close contact with COVID-19 patients was also associated with an increased risk, particularly during prolonged contact (>15 min.). Items associated with a lower risk were respirators during aerosol-generating procedures and gloves, gowns or coveralls during contact with contaminated materials/surfaces. No difference was observed among health workers using respirators versus surgical masks for routine care.
Appropriate implementation of infection prevention and control measures and PPE use remain a priority to protect health workers from SARS-CoV-2 infection.