key: cord-0696465-jz1gis7y authors: Schwartz, Kevin L.; Muller, Matthew P.; Williams, Victoria; Harry, Robin; Booker, Sonya; Katz, Kevin; Leis, Jerome A. title: Coronavirus disease 2019 (COVID-19) risk among healthcare workers performing nasopharyngeal testing date: 2021-08-02 journal: Infect Control Hosp Epidemiol DOI: 10.1017/ice.2021.354 sha: 521aaf6c19dbad26985448c2a9278b2b2fafd652 doc_id: 696465 cord_uid: jz1gis7y nan worked in a patient-facing role and regularly performed nasopharyngeal swabs or examine patients, compared to CAC HCWs (eg. administrative staff) who had no patient contact. The primary outcome was evaluated using the χ 2 test. Based on our fixed sample size, using a 2-sided α of 0.05, we had a power of 80% to detect a difference of 2%. A Poisson regression model with a generalized estimating equation was created for the secondary analysis that accounted for clustering among HCWs at the same CAC. As a sensitivity analysis, the primary outcome was compared again based on a study period ending December 31, 2020, prior to the start of COVID-19 vaccination of HCWs. Research ethics review was not required because the study met criteria for exemption; the project was deemed improvement in quality and not human-subject research. During the study period, 354,027 patients were tested across the 4 CACs, and 21,951 (6.2%) were confirmed positive for SARS-CoV-2, including 4,097 (4.3%), 2,830 (3.8%), 4,887 (5.8%) and 10,137 (10.1%) at the 4 CACs. Table 2 summarizes the outcomes of 470 HCWs working in the CACs. Overall HCW positivity rate for SARS CoV-2 was 2.3% (11 of 470) compared to 2.2% in the Ontario population (P = .82). We detected no significant difference in the rate of HCW infections between patient-facing and nonpatient-facing roles, with 2.3% and 2.2% of HCWs positive, respectively (relative risk, 0.89; 95% confidence interval [CI], 0.49-1.65; P = .72). In the sensitivity analysis, the overall HCW positivity rate for SARS CoV-2 was 1.7% (8 of 470) compared to 1.2% in the rest of Ontario (P = .34). Our results show that when embedded within a comprehensive bundle of measures designed to minimize COVID-19 transmission, the use of surgical masks was effective in protecting HCWs given a rate of infection similar to a population average that included nonessential workers. The similar infection rates between clinical and nonclinical staff suggest that most infections that did occur were likely acquired outside the CACs. Variability in practice exists regarding whether surgical masks or N95 respirators are used for routine care of suspected or confirmed COVID-19 patients, including during testing for SARS-CoV-2. A recent systematic review reported limited to no evidence regarding the risk of aerosol transmission related to nasopharyngeal or oropharyngeal swabs in the detection of SARS-CoV-2. 9 Our study helps to address this important gap in the literature and supports existing international guidelines recommending droplet and contact precautions for this specimen collection. This study has several limitations. It was limited by the observational design and small sample size. There were differences in the number of HCWs and the relative time working at each CAC, which may have affected the exposure risk between sites. We attempted to account for clustering within sites using generalized estimating equation model in the secondary analysis. The patient population had a test positivity rate of 6% and generally exposures during testing were brief. However, a detectable difference in SARS-CoV-2 infection risk would be expected if these practices were inadequate, given that these HCWs were within close contact to nearly 22,000 patients with COVID-19, have similar or higher expected nonoccupational risks for COVID-19 compared to the general population, and are more likely to be tested. 10 Our findings provide supporting evidence for the effectiveness and safety of this combination of infection prevention and control measures, which includes PPE of a surgical mask, eye protection, gown, and gloves in the collection of nasopharyngeal and oropharyngeal swabs for SARS-CoV-2. Engineering controls -Assessment and optimization of HVAC system (see specific air exchanges) Administrative controls -Distancing of 2 m between patients upon entry to clinic and waiting room -Partition at registration desk -All nasopharyngeal testing in private room or behind partition -Alcohol-based hand rub available at point of care -Training of patient-facing staff in personal protective equipment donning and doffing and nasopharyngeal swab collection -Environmental cleaning between patients -Daily active screening of HCWs for symptoms, unprotected exposures and travel history with exclusion from work and testing when symptom positive and/or high risk exposure a -Contact tracing of positive HCWs -Distancing in break rooms Patient -Masking at all times except during nasopharyngeal testing Healthcare worker without patient contact -Surgical mask Healthcare worker performing nasopharyngeal testing -Surgical mask -Eye protection (face shield or goggles) -Gown -Gloves Note. HVAC, heating, ventilation and air conditioning; HCW, healthcare worker. a High-risk exposure defined as any close contact (within 2 m) with unmasked individual for 10-minutes or longer where HCW was either not wearing a mask, or eye protection, or both. Note. CAC, COVID-19 assessment center; HCW, healthcare worker. How does COVID-19 spread between people? World Health Organization website Airborne transmission of SARS-CoV-2: theoretical considerations and available evidence Characteristics associated with household transmission of SARS-CoV-2 in Ontario, Canada: a cohort study SARS-CoV-2 transmission from people without COVID-19 symptoms Ontario Ministry of Health COVID-19 provincial testing guidance update v. 11.0. Ontario Ministry of Health website The National Institute for Occupational Safety and Health (NIOSH) Risk of dispersion or aerosol generation and infection transmission with nasopharyngeal and oropharyngeal swabs for detection of COVID-19: a systematic review Epidemiology, clinical characteristics, household transmission, and lethality of severe acute respiratory syndrome coronavirus-2 infection among healthcare workers in Ontario Acknowledgments. We thank staff working at the CAC, particularly in infection prevention and control and occupational health and safety, at all participating sites. We especially thank Nicholas Tomiczek of Sunnybrook Health Sciences Centre for helping to collate healthcare worker outcome data for this site.Financial support. No financial support was provided relevant to this article. None of the authors have any conflicts of interest to disclose. Dr Jerome Leis has received remuneration outside of the present work, from the Ontario Hospital Association and Ministry of the Attorney General of Ontario for expert testimony regarding Infection Prevention and Control of COVID-19.