Seroprevalence of SARS-CoV-2 Among Frontline Health Care Personnel in a Multistate Hospital Network

13 Academic Medical Centers, April-June 2020

Wesley H. Self, MD; Mark W. Tenforde, MD, PhD; William B. Stubblefield, MD; Leora R. Feldstein, PhD; Jay S. Steingrub, MD; Nathan I. Shapiro, MD; Adit A. Ginde, MD; Matthew E. Prekker, MD; Samuel M. Brown, MD; Ithan D. Peltan, MD; Michelle N. Gong, MD; Michael S. Aboodi, MD; Akram Khan, MD; Matthew C. Exline, MD; D. Clark Files, MD; Kevin W. Gibbs, MD; Christopher J. Lindsell, PhD; Todd. W. Rice, MD; Ian D. Jones, MD; Natasha Halasa, MD; H. Keipp Talbot, MD; Carlos G. Grijalva, MD; Jonathan D. Casey, MD; David N. Hager, MD, PhD; Nida Qadir, MD; Daniel J. Henning, MD; Melissa M. Coughlin, PhD; Jarad Schiffer, MS; Vera Semenova, PhD; Han Li, PhD; Natalie J. Thornburg, PhD; Manish M. Patel, MD


Morbidity and Mortality Weekly Report. 2020;69(35):1221-1226. 

In This Article


Among a convenience sample of HCP who routinely cared for COVID-19 patients in 13 U.S. academic medical centers from February 1, 2020, 6% had evidence of previous SARS-CoV-2 infection, with considerable variation by location that generally correlated with community cumulative incidence. Among participants who had positive test results for SARS-CoV-2 antibodies, approximately one third did not recall any symptoms consistent with an acute viral illness in the preceding months, nearly one half did not suspect that they previously had COVID-19, and approximately two thirds did not have a previous positive test result demonstrating an acute SARS-CoV-2 infection. These findings suggest that some SARS-CoV-2 infections among frontline HCP are undetected and unrecognized, possibly because of the minimally symptomatic or subclinical nature of some infections, underreporting of symptoms, or nonsystematic testing of some personnel with symptomatic infections.

This study resulted in the identification of two factors potentially associated with SARS-CoV-2 infection among HCP: PPE shortages and interacting with patients without wearing a face covering. These findings highlight the importance of maintaining PPE supplies at hospitals caring for COVID-19 patients and, assuming adequate supply, adhering to policies that encourage the use of masks for all interactions between HCP and patients. Universal masking has been associated with a significantly lower rate of infection among HCP.[9]

The findings in this report are subject to at least four limitations. First, bias might have occurred if personnel at higher or lower risk for infection were less or more likely to volunteer to participate; for example, HCP not working because of illness or quarantine were not recruited and might have been at higher risk for SARS-CoV-2 infection. Second, seroprevalence could be underestimated if participants who were infected had not yet mounted an antibody response or if antibody titers had declined since infection.[10] Third, information on facility-level infection prevention and control practices that could further affect exposure risk was not collected. Also, multivariable models to adjust for confounding were not performed. Finally, among seropositive HCP, exposure that led to SARS-CoV-2 infection could have occurred within the hospital setting or the community and this study could not distinguish between these potential sources of exposure. In general, seroprevalence among HCP across sites correlated with community COVID-19 incidence. SARS-CoV-2 exposures in the hospital could also have occurred between health care providers (e.g., within shared workspaces).

Evidence of previous SARS-CoV-2 infection was detected in 6% of frontline HCP from 13 academic medical centers within the first several weeks of U.S. transmission, although prevalence varied considerably by location. A high proportion of personnel with antibodies did not suspect that they had been previously infected. The risk for transmission of SARS-CoV-2 from HCP to others within hospitals might be mitigated by adherence to recommended practices such as universal use of face coverings and suggestions to have dedicated cohorts of HCP caring for patients with COVID-19. In addition to maintaining PPE supplies and instituting universal face covering policies for HCP at work, enhanced screening, including frequent testing of frontline HCP, and universal use of face coverings in hospitals are strategies that could reduce SARS-CoV-2 transmission.