UVA: Herd immunity a long way off without vaccines
CHARLOTTESVILLE, Va. (WDBJ/UVA Release) - UVA researchers have concluded herd immunity in Virginia is “currently not a plausible means of ending the COVID-19 pandemic.” But they believe their finding underscores the importance of vaccines, saying without them, herd immunity is that much further off.
The finding is based on a study in which statewide blood testing for COVID-19 found only 2% of Virginians had antibodies to the virus as of mid-August 2020, just months after the pandemic began and before vaccines were available.
About 2.8 times more Virginians had antibodies than had been identified by the state’s PCR testing, according to UVA researchers. 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, according to UVA, 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.”
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 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, according to UVA
Among the 101 participants who were found to have COVID-19 antibodies, 42 were Hispanic. People with antibodies were more likely to live in multifamily units and had contact with a patient confirmed to have COVID-19, the researchers report.
The researchers estimated approximately 66% of the detected infections were asymptomatic.
Prior COVID-19 studies have suggested 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, according to UVA.
“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.”
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