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

Abstract

Background: 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.

Methods: 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.

Findings: 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.

Conclusion: Appropriate implementation of infection prevention and control measures and use of PPE remain a priority to protect health workers from SARS-CoV-2 infection.

Keywords: Adherence; COVID-19; Health workers; Infection prevention and control; Occupational risk factors; Personal protective equipment; SARS-CoV-2.

Figure 1

Characteristics of study participants enrolled. (A) Countries (pink) and healthcare facilities (green) where participants were enrolled. Numbers of enrolled participants are represented in shades of pink. (B) Number of participant enrolments over time. (C) Study participants enrolled and reasons for exclusion from the main analysis. Participants excluded from the main analysis could have had more than one reason for exclusion. PCR, polymerase chain reaction.

Figure 2

Risk factors associated with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection among health workers during high-risk procedures from multi-variable logistic regression results. (A) After direct close contact (within 1 m) with coronavirus disease 2019 (COVID-19) patients. (B) After exposure to COVID-19 patient materials (e.g. clothing). (C) After exposure to surfaces (e.g. bed, dining table) around COVID-19 patients. Confounders included in the multi-variable regression but not presented in the plot include: used public transport during 14 days prior to completing the first questionnaire; had social contact outside of work during 14 days prior to completing the first questionnaire; adherence to personal protective equipment guidelines; exposure to SARS-CoV-2 infection outside of work; and received in-person infection prevention and control training. X-axis represents the adjusted odds ratio (log scale). Horizontal bars represent 95% confidence intervals. Green points represent the adjusted odds ratio estimates. Odds ratio values from both univariable and multi-variable analyses are included in supplementary appendix (Tables 3.3–3.5).

Figure 3

Personal protective equipment items and risk of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection during high-risk procedures. Three vertical panels refer to, from left to right, aerosol-generating procedures, prolonged close contact >15 min (excluding aerosol-generating procedures), and contact with contaminated materials or surfaces. Number of participants who had these high-risk exposures and had matched cases/controls from the same healthcare facility are indicated in brackets. Horizontal panels refer to the different types of mask, including respirators and surgical masks; eye protection, including goggles and face shields; gloves; and gowns or coveralls. Grey squares indicate odds ratios for wearing each item of personal protective equipment and risk of SARS-CoV-2 infection during each high-risk exposure. The accompanying horizontal grey bars indicate 95% confidence intervals for each odds ratio. The categorical variable, respirator/surgical mask, was given a value of 1 when participants chose both respirator and surgical mask options for the question on which items of personal protective equipment were worn during the respective procedures. The vertical red dashed line highlights an odds ratio of 1. Confounders included in the above multi-variable regression analyses, but not presented in the graph, include adherence to personal protective equipment guidelines, hand hygiene adherence, and received in-person infection prevention and control training.