Over 80 pct of American adults now have COVID-19 antibodies: Blood donor study

New blood donor research suggests that more than 80 percent of American adults now have COVID-19 antibodies due to vaccinations or infections.

Published in the open-access medical journal JAMA on Thursday, the study estimated that more than 80 percent of Americans above 16 years of age had COVID-19 antibodies as of May 2021. The results were based on previously collected data from blood donors.

The authors of the study cautioned that while this was the case in the context of their study, the results might not be generalizable to the entire population of the US, online news media Gizmodo reported on Friday.

The team of researchers has been analyzing samples of donated blood across the US every month since July 2020, searching for antibodies specific to the coronavirus.

Taken from 50 states, areas that represented around 74 percent of the US’s population, the samples were used as a baseline for the estimate. In July 2020, they found that 3.5 percent of Americans over 16 had antibodies to the virus.

This percentage seemed to increase by May 2021, according to their findings which indicated a rate of 20.2 percent.

After the country’s vaccination campaign was rolled out in December 2020, the team added a second test to differentiate between antibodies gained through vaccination and infection. They collected almost 1.5 million blood specimens by May 2021.

When combining both types of immunity, the scientists estimated that around 83 percent of adults had COVID-19 antibodies overall.

“Based on a sample of blood donations in the US from July 2020 through May 2021, vaccine- and infection-induced SARS-CoV-2 seroprevalence increased over time and varied by age, race, and ethnicity, and geographic region,” the study’s authors wrote.

However, the study’s findings come with important limitations to consider.

“Despite weighting to adjust for demographic differences, these findings from a national sample of blood donors may not be representative of the entire US population,” they wrote.

Those who were willing to donate blood might have been different from the general public in relevant ways. Their likelihood of getting infected or getting vaccinated might have differed.

Also, it is important to consider that millions of people have been vaccinated against or infected with COVID-19 since the end of May, indicating that the true current percentage of American adults with antibodies could be lower in reality.

According to the US’s Centers for Disease Control and Prevention (CDC), as of September 3 over 175.5 million Americans have been fully vaccinated- around 53 percent of the population.

The research is expected to continue until at least December 2021, the scientists said, adding that the results will then be published on the CDC’s website.