More than 80% of Americans have coronavirus antibodies acquired through infection or vaccination, according to a new study of over 1.4 million blood donations across the U.S.
The study, published Thursday in the journal JAMA, included blood samples of Americans 16 and older collected by 17 different organizations from all 50 states, Washington, D.C. and Puerto Rico. Donations represent 74% of the U.S. population, researchers said.
Estimates show that from July to December 2020 — before vaccines were available — the percentage of Americans 16 years or older with coronavirus antibodies from infection jumped from 3.5% to 11.5%. By May 2021, the percentage of Americans with infection-derived antibodies increased to about 20%.
But when researchers combined the number of people with antibodies from either infection or vaccination, they found about 83% of Americans had earned them. (Federal health officials authorized the first COVID-19 vaccine on Dec. 14, 2020).
Hispanic and Black people were the most likely to have antibodies from infection, a finding consistent with case trends since the pandemic started. By May 2021, however, more Asian and white people had coronavirus antibodies from either infection or vaccination, likely because these groups received vaccinations at greater rates than Hispanic and Black people.
Adults aged 65 and older were the least likely to have antibodies from infection, the study found. Researchers say that data could be explained by their weaker immune systems being unable to develop antibodies or their greater participation in COVID-19 preventive behaviors, such as physical distancing and mask wearing, compared to younger people.
Researchers note their analysis was done before the delta variant rose to dominance in the U.S. and triggered a fourth wave of infections. Many more people have been vaccinated since data collection, too, suggesting the study’s estimates may be higher than reported.
More than 175.5 million Americans are fully vaccinated as of Sept. 3, according to a Centers for Disease Control and Prevention tracker — about 53% of the total population.
The study also excluded blood donations from people younger than 16, meaning much remains unknown about the prevalence of antibodies in younger people.
The research will continue until at least December 2021, the researchers said. Results will be posted on the CDC website.
More than 39.6 million people have contracted the coronavirus in the U.S. as of Sept. 3, a Johns Hopkins tracker shows, and nearly 645,000 people have died.