Reviewed by Valeria Fabre, MD; Johns Hopkins University School of Medicine and S. Shaefer Spires, MD; Duke University School of Medicine
Two recent epidemiologic studies describe the risk of SARS-CoV-2 infection in healthcare workers (HCW) associated with exposures in the hospital and at home. First, Baker and colleagues report on COVID-19 risk among HCW who were exposed to a patient who wasn’t diagnosed with COVID-19 until hospital day 13. Exposure was defined as ≥10 cumulative minutes of face-to-face contact within 6 feet. HCWs began wearing surgical masks 7 days into the patient’s hospitalization, based on a hospital policy for universal masking. Exposure was estimated based on employee’s self-reports, nurse manager assessment, and medical record review. Forty-four HCWs were exposed and offered nasopharyngeal PCR testing, 8 of them developed symptoms, of whom only 3 tested positive for COVID-19. Of the 3 HCWs who tested positive, one was exposed to a household member with confirmed COVID-19. The other 2 HCWs had 60-70 minutes of cumulative exposure to the patient respectively within the 14 days preceding their infections. Specifically, one HCWs spent ~60 minutes cumulatively helping to bathe, reposition, and reorient the patient, much of this time unmasked. The other provider placed a nasogastric tube that caused the patient to cough and gag.
Second, Steensels and colleagues describe their investigation of the prevalence of IgG antibodies against SARS-CoV-2 among hospital staff in a Belgium tertiary care center. Antibodies directed to the nucleocapsid protein of SARS-CoV-2 were detected and internal validation of the assay found a sensitivity of 92.2% and specificity of 97.0% for this IgG. IgM results were excluded due to poor sensitivity (57.9%) and staff with active symptoms were not tested. Being involved in clinical care, having worked during the lockdown phase, being involved in case for patients with COVID-19 and exposure to COVID-19 positive coworkers were not statistically significantly associated with seroprevalence. However, having a household contact with suspected or confirmed COVID-19 was associated with antibody positivity (81/593 [13.7%] household contact vs 116/2435 [4.8%] without household exposure; p<0.001), with an odds ratio of 3.15 (95% CI, 2.33-4.25). Prior anosmia was associated with the presence of antibodies, OR of 7.78 (95% CI, 5.22-11.53).
In summary, despite substantial exposure to a patient with COVID-19 without adequate personal protective equipment, <5% of exposed healthcare personnel tested positive for SARS-CoV-2. These data agree with other observations reporting the transmission of SARS-CoV-2 to HCW in the workplace appears to be low. This finding may be explained by the fact that HCW may be more “thoughtful” about hand hygiene or maintaining 6 feet distance in the hospital setting than during social activities outside of work or at home. In addition, many hospitals have since implemented universal masking ± universal face shield for patient interactions which appears effective at reducing transmission as described above in the second study. Anecdotally, US hospitals attribute healthcare associated COVID-19 infections to be secondary to exposure to co-workers rather than patients.