Health Care Worker Seroprevalence Data Show Undetected COVID-19 Spread

Much remains to be seen about the precise prevalence and clinical characteristics of SARS-CoV-2 infection among US health care workers. It is likely, however, that being employed in a health care setting poses unique risks.

A new US Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report (MMWR) adds new information on the seroprevalence of SARS-CoV-2 among health care workers in a 13-hospital multistate medical network between April and June of 2020.

MMWR authors emphasized that those who care for patients with coronavirus disease 2019 (COVID-19) are at risk for exposure and can spread SARS-CoV-2 to patients, coworkers, and others in the community.

From April 3-June 19, samples were collected at 13 geographically dispersed academic medical centers. Antibody testing was performed with an enzyme-linked immunosorbent assay against the extracellular domain of the SARS-CoV-2 spike protein.

Among 3248 participating health care workers, 1445 were nurses, 919 were physicians, nurse practitioners, or physician assistants, 235 were respiratory therapists, and 649 had other clinical roles.

The median age of health care workers was 36 years of age, and 80% reported no underlying conditions.

There were important demographic data collected as well: seropositivity was lower among women (5.3%) than among men (7.2%) and among non-Hispanic White participants (4.4%) than among participants of other racial/ethnic groups (9.7%).

Among the total of 3248 health care workers, 6% had clear antibody evidence of prior infection, but seroprevalence ranged from 0.8% all the way to 31.2%.

Among these 6% of personnel, 29% were asymptomatic in previous months and 69% had never been diagnosed with SARS-CoV-2.

A high number of SARS-CoV-2 infections in health care workers thus appears to go undetected, in part due to milder severity among those of working age.

Interestingly, MMWR authors also report that prevalence of SARS-CoV-2 antibodies was lower among those who reported always wearing a face covering while caring for patients (6%) compared with those who did not (9%). But face masks, of course, were not a silver bullet:

“Use of a face covering during all clinical encounters in the week preceding enrollment was reported by 2,904 (89%) participants.”