New research indicates that more than 80% of American adults now have antibodies to coronavirus, obtained from infection or vaccination. The study, based on data collected from blood donors, estimates that more than 80% of Americans over the age of 16 had these antibodies in May 2021. However, the authors warn that their results may not be generalizable. for the entire American population. .
The study, published Thursday at JAMA, is the work of researchers from various blood donation organizations, as well as the pandemic response group of the Centers for Disease Control and Prevention.
Each month, as of July 2020, the team has been analyzing blood samples collected from people over the age of 16 in the United States, looking for covid-19-specific antibodies. The samples were taken from 50 states, from areas that represent approximately 74% of the country’s population. After starting the vaccination campaign in December 2020, the team added a second test to differentiate the positive results from the antibodies as the infection or vaccine is induced (both vaccination and infection force the body to produce antibodies against the ear protein of the virus, but the infection also generates a response to other parts of the virus). By May 2021 they had already collected just under 1.5 million blood copies.
Using these samples as a reference, they estimated that 3.5% of Americans over the age of 16 had antibodies to the virus by July 2020, even infected. In May 2021, the percentage of Americans with these infection-induced antibodies was estimated to be 20.2%. And by combining both types of immunity, they estimated that 83.3% of adults had antibodies in general.
“Based on a sample of blood donations in the United States from July 2020 to May 2021, the seroprevalence of vaccine-induced SARS-CoV-2 and infection increased over time and varied according to age, race and ethnicity and geographical region, “the authors wrote. .
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The results have some important limitations. People willing to donate blood may differ from the general public in relevant ways that could affect their likelihood of becoming infected or getting vaccinated later. And because, in the first place, you have to be over 16 years old to donate blood, that can’t tell us anything about the prevalence of antibodies in younger people. Antibody testing is also not flawless and some unfortunate people may not generate it detectable antibodies after infection or vaccination, while some antibodies may decrease to undetectable levels over time (although the jury still does not know how often this occurs). Immunity is also more complicated than just having the right antibodies.
Finally, since the end of May, there have been millions there are more vaccinated or infected people, meaning the team estimate is probably lower than the actual actual percentage of American adults with antibodies.
The authors attempted to account for possible differences between blood donors and the general public in making their estimates. But they acknowledge that their math could have fallen short.
“Despite the weighting to adjust for demographic differences, these findings from a national sample of blood donors may not be representative of the entire U.S. population,” they wrote.
With all this in mind, these figures should be considered as a summary of our collective immunity to coronavirus, not as an exact figure. But yes show that vaccines have greatly accelerated the process of Americans with some degree of immunity to the virus, while offering highly effective protection against the worst results of coming face to face with covid-19. The risk of hospitalization, death, even long-term symptoms it is substantially lower in the vaccinated than in the unvaccinated and unexposed. Unfortunately, the results also suggest that millions of Americans are still at risk of contracting the virus without pre-existing immunity.
The team plans to monitor the prevalence of coronavirus antibodies among blood donors until December 2021.