SARS-CoV-2 infections among healthcare workers may go undetected

Sept. 2, 2020

A high proportion of SARS-CoV-2 infections among healthcare personnel appear to go undetected, the Centers for Disease Control and Prevention (CDC) noted, based on the results of a study reported in Morbidity and Mortality Weekly Report (MMWR).

To conduct the study, researchers collected blood serum specimens between April 3–June 19, 2020, from frontline healthcare personnel who worked with COVID-19 patients at 13 geographically diverse academic medical centers in the United States, and specimens were tested for antibodies to SARS-CoV-2. Participants were asked about potential symptoms of COVID-19 they experienced since February 1, 2020, previous testing for acute SARS-CoV-2 infection, and their use of personal protective equipment (PPE) in the past week.

Among 3,248 personnel observed, 6 percent had antibody evidence of previous SARS-CoV-2 infection; 29 percent of personnel with SARS-CoV-2 antibodies were asymptomatic in the preceding months, and 69 percent had not previously received a diagnosis of SARS-CoV-2 infection. Seroprevalence by hospital ranged from 0.8 percent to 31.2 percent, with a median of 3.6 percent.

Prevalence of SARS-CoV-2 antibodies was lower among personnel who reported always wearing a face covering (defined in this study as a surgical mask, N95 respirator, or powered air purifying respirator [PAPR]) while caring for patients (6 percent), compared with those who did not (9 percent).

“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,” the CDC said.

The study was conducted by the Influenza Vaccine Effectiveness in the Critically Ill (IVY) Network, which is a collaboration of academic medical centers in the United States conducting epidemiologic studies on influenza and COVID-19.

The CDC received serum specimens and completed testing for SARS-CoV-2 antibodies with an enzyme-linked immunosorbent assay against the extracellular domain of the SARS-CoV-2 spike protein. This assay uses anti-pan–immunoglobulin (Ig) secondary antibodies that detect any SARS-CoV-2 immunoglobulin isotype, including IgM, IgG, and IgA.

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