Study Suggests Virginia is a Long Way from Herd Immunity

Feb 18, 2021

More than half a million Virginians have been diagnosed with COVID-19, and many more could have been infected without developing symptoms.  The state also reports vaccinating more than a million people.

So are we getting close to what’s known as herd immunity? 

In August the University of Virginia looked at blood drawn from more than 5,000 patients who had gone to the doctor for something other than COVID-19.  Fewer than three percent had antibodies to the virus. 

Credit CDC

Using that as a baseline, Dr. Eric Houpt, chief of UVA’s Division of Infectious Diseases, was able to calculate the number of people who might now be carrying some degree of immunity. “Fifteen to 20% would be our prediction, and that’s still too low for herd immunity,” Houpt noted.

To get there, he says, many more people need to get their shots. “We’ll see herd immunity when there’s enough people vaccinated that the virus can’t spread effectively anymore.”

Until then, he advises people to keep wearing masks even if they’ve been vaccinated.  That’s because vaccine does a good job of preventing cases of COVID with symptoms but it might not keep you from getting an asymptomatic case and spreading the virus to others.

“The studies have not been done to examine whether it reduces asymptomatic infections," Houpt said. "Maybe they’re protected against getting symptomatically ill, but they could still carry it.”

In the UVA study last summer, 66% of people who had antibodies to COVID-19 had not developed symptoms of the disease.