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February 15, 2021

COVID-19 Antibody Testing Suggests Large Majority of Virginians Vulnerable to Virus

Eric Houpt in his lab.

Statewide blood testing for COVID-19 has found that only 2% of Virginians had antibodies to the virus as of mid-August. The result has prompted the researchers to conclude that herd immunity in Virginia is “currently not a plausible means of ending the COVID-19 pandemic.”

Approximately 2.8 times more Virginians had antibodies than had been identified by the state’s PCR testing, the researchers report. That ratio is lower than many estimates predicting how much of the country’s population may already have COVID-19 antibodies. 

Hispanic study participants had the highest exposure rate, with more than 10% having antibodies. Other groups with “notably higher” rates included Northern Virginia residents (4.4%), those aged 40 to 49 (4.4%) and the uninsured (5.9%). Prevalence by zip code ranged from 0% to 20%. Often, neighboring zip codes produced dramatically different results, the researchers say.

“We carefully follow case counts but need to recognize case counts are an underestimate of the true number of COVID infections,” said Eric Houpt, MD, the chief of UVA Health’s Division of Infectious Diseases and International Health. “If we use these data to project to today, we would project that as of February 2021, still under 20% of Virginians may have been exposed to the virus.”

The findings underscore the need for Virginians to get vaccinated to protect themselves from the virus, Houpt said.

COVID-19 Antibody Testing

To better understand how widespread COVID-19 has been in Virginia, UVA Health and the Virginia Department of Health partnered with large ­­hospitals around the state. The researchers tested the blood of 4,675 outpatients at five geographically diverse health systems: UVA Health in the northwest, Inova Health System in the north, Sentara Healthcare in the east, Carilion Clinic in the southwest and Virginia Commonwealth University in the central. Each site enrolled up to 1,000 residents, aged 18 or older, who were not being evaluated for potential COVID-19 infections.  Participants matched the age, race and ethnicity makeup of each region.

Among the 101 participants who were found to have COVID-19 antibodies, 42 were Hispanic. People with antibodies were more likely to live in a multifamily unit and had contact with a patient confirmed to have COVID-19, the researchers report.

The researchers estimated that approximately 66% of the detected infections were asymptomatic.

Prior COVID-19 studies have suggested that confirmed cases may represent only a small percentage of the people who have been infected. Estimates of total unrecognized infections have ranged from six times the confirmed cases to 53 times, so the results from Virginia were lower in comparison.

“Virginians are still quite susceptible to this virus,” Houpt said. “We need to continue wearing masks in public and practice social distancing and hand washing. I encourage everyone who qualifies to get a COVID vaccine when they can.”

About the Research

The researchers have published their findings in the scientific journal JAMA Network Open. The research team consisted of Elizabeth T. Rogawski McQuade, Kristin A. Guertin, Lea Becker, Darwin Operario, Jean Gratz, Dave Guan, Fauzia Khan, Jennifer White, Timothy L. McMurry, Bhruga Shah, Stephanie Garofalo, Matt Southerland, Kelly Bear, John Brush, Cynthia Allen, Amy Frayser, Rebecca Vokes, Rashmi Pershad, Lilian Peake, Christopher deFilippi, Kathleen Barackman, Gonzalo Bearman, Andrea Bidanset, Francis Farrell, David Trump and Eric R. Houpt.

The study was supported by the Virginia Department of Health with funds from the U.S. Coronavirus Relief Fund. A full list of the authors’ disclosures is included in the paper.

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