Infection prevention and control risk factors for SARS-CoV-2 infection in health workers: a global, multi-centre, case–control study

Health workers were at higher risk for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection during the coronavirus disease 2019 (COVID-19) pandemic due to occupational risk factors. This study aimed to characterize these risk factors as part of the World Health Organization (WHO) Unity Studies initiative. This global, multi-centre, 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 documented occupational exposure to COVID-19 patients in the 14 days pre-enrolment. Controls were enrolled from the same facilities with 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. Risk of SARS-CoV-2 infection was associated with non-adherence to personal protective equipment (PPE) guidelines [adjusted odds ratio (aOR) 1.67, 95% confidence interval (CI) 1.32–2.12] and not performing hand hygiene consistently after patient contact (aOR 2.52, 95% CI 1.72–3.68). Direct close contact with COVID-19 patients was also associated with increased risk of SARS-CoV-2 infection, particularly during prolonged contact (>15 min). Items associated with lower risk of SARS-CoV-2 infection were use of a respirator during aerosol-generating procedures; and use of gloves, and a gown or coverall during contact with contaminated materials/surfaces. No difference was observed between health workers using respirators vs surgical masks for routine care. Appropriate implementation of infection prevention and control measures and use of PPE remain a priority to protect health workers from SARS-CoV-2 infection.