Health care workers working on COVID-19 wards at increased risk for nosocomial SARS-CoV-2 infection

1. The risk of SARS-CoV-2 infection was nearly 4-fold higher among health care workers working on COVID-19 inpatient wards compared to workers not in patient care, suggesting increased risk from nosocomial infection in this population.

2. Combined phylogenetic and epidemiological analyses found no patient-to-health care worker transmission but several health care worker-to-health care worker transmission clusters.

Evidence Rating Level: 2 (Good)

Study Rundown: Throughout the COVID-19 pandemic, health care institutions worldwide were tasked with the difficult responsibility of balancing the treatment of patients with COVID-19 and protecting and preventing the spread of COVID-19 among other patients, visitors, and health care workers (HCWs). Amidst stringent infection prevention and control measures, HCWs have nonetheless become infected during provision of care for patients with COVID-19. However, transmission dynamics concerning when, where, and by whom HCWs working in health care facilities were infected with SARS-CoV-2 are largely unclear. This cohort study, the Serologic Surveillance of SARS-CoV-2 Infection in Health Care Workers (S3), sought to quantify the incidence of nosocomial SARS-CoV-2 infection among HCWs, risk stratifying by varying amounts of exposure to patients with COVID-19 and identifying potential transmission clusters in 2 tertiary care centers in the Netherlands. The main endpoint of the analysis was cumulative incidence of and time to SARS-CoV-2 infection, defined as the presence of SARS-CoV-2-specific antibodies in serial serologic measurements. This data was used in combination with epidemiological data and phylogenetic analysis of viruses isolated from patients and HCWs to identify transmission clusters. Among 801 HCWs, the risk of SARS-CoV-2 infection was nearly 4-fold higher with HCWs working on COVID-19 inpatient wards compared to HCWs not in patient care. Furthermore, combined phylogenetic and epidemiological analyses found no patient-to-HCW transmission but several HCW-to-HCW transmission clusters. These results suggested that HCWs working on COVID-19 inpatient wards are at increased risk for nosocomial SARS-CoV-2 infection where HCW-to-HCW transmission played a significant role. A limitation of this study was the potential presence of selection bias within the exposed cohort as symptomatic HCWs in quarantine were not able to enroll if the absence occurred during the first serial serological measurement. Despite the prospective cohort design of this study to limit bias (compared to most studies that are cross-sectional or retrospective), this may have resulted in an underestimation of cumulative incidence.

Click to read the study in JAMA Network Open

Relevant Reading: Differential occupational risks to healthcare workers from SARS-CoV-2 observed during a prospective observational study

In-Depth [prospective cohort]: This cohort study included 801 HCW participants (median [IQR] age, 36 [29-50] years; 580 [72.4%] women) who underwent 4 weekly measurements of SARS-CoV-2-specific antibodies and collection of questionnaires between March and June 2020, in combination with phylogenetic and epidemiologic transmission analyses at 2 university hospitals in the Netherlands. Data analysis was completed between August and December 2020. Among HCWs, 439 were working in patient care for those with COVID-19, 164 were working in patient care for those without COVID-19, and 198 were not working in patient care. The incidence of SARS-CoV-2 was highest among HCWs working in patient care for those with COVID-19 (54 HCWs [13.2%; 95%CI, 9.9%-16.4%]), followed by HCWs working in patient care for those without COVID-19 (11 HCWs [6.7%; 95%CI, 2.8%-10.5%]; HR, 2.25; 95% CI, 1.17-4.30), followed by HCWs not working in patient care (7 HCWs [3.6%; 95%CI, 0.9%-6.1%]; HR, 3.92; 95%CI, 1.79-8.62). Further stratifying risk among HCWs caring for patients with COVID-19, SARS-CoV-2 cumulative incidence was highest among those working on COVID-19 inpatient wards (32/134 HCWs [25.7%; 95%CI, 17.6%-33.1%]), followed by those working in intensive care (13/186 HCWs [7.1%; 95%CI, 3.3%-10.7%]; HR, 3.64; 95%CI, 1.91-6.94), followed by those working in emergency departments (7/102 HCWs [8.0%; 95%CI, 2.5%-13.1%]; HR, 3.29; 95%CI, 1.52-7.14). Finally, 3 potential HCW-to-HCW transmission clusters and no patient-to-HCW transmission clusters were identified via epidemiologic data combined with phylogenetic analyses on COVID-19 wards.

Image: PD

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