Between mid-June 2020 and early March 2021, the American Red Cross tested more than 3.3 million donations from unvaccinated people in 44 states for the presence of Covid-19 antibodies. Overall, around 7.5% of donations tested during this period were positive for Covid-19 antibodies, meaning donors had likely been infected with the coronavirus at some point.
The American Red Cross notes that “a positive antibody test result does not confirm infection or immunity,” but it can indicate whether a person has been exposed to the coronavirus, “regardless of whether an individual has developed symptoms ”. The prevalence of antibodies in unvaccinated blood donors has increased over time, as cases have increased across the country.
According to data shared with CNN via email, around 1.5% of donations tested in the first week of July were positive for Covid-19 antibodies. This rose to almost 4% of donations tested in the first week of October, around 12% of donations tested in the first week of January, and almost 21% of donations tested in the first week of March.
“Blood donors are not a random sample of the general population, but they are interesting,” said Dr. William Schaffner, longtime U.S. Centers for Disease Control and Prevention advisor on vaccines.
“The first is that a substantial portion of the American population has known about Covid, at least the blood donor population, knowingly or not. The other is that a huge proportion of the American population didn’t – that’s the 80%, ”he said. . “So we can’t just rely on the strategy of letting the herd immunity happen naturally. We need to vaccinate so that up to 80% of the population is immune. ”
Herd immunity is the point at which enough people are protected against a disease that they cannot spread in the population. This can be done when a sufficient number of individuals have antibodies against the virus.
People who recover from the coronavirus enjoy some protection against the virus, although scientists still do not know how long it lasts or how robust it is against emerging variants of the coronavirus. Getting a Covid-19 vaccine stimulates the immune system to artificially provide protection.
“Both contribute to the goal of reaching 80%,” Schaffner said.
The percentage of the U.S. population that must be vaccinated for the country to achieve collective immunity remains “an elusive number,” Dr.Anthony Fauci, chief medical adviser to President Joe Biden, told a House briefing White Monday.
“We shouldn’t be so obsessed with this elusive number of collective immunities. We should just be concerned about getting as many people vaccinated as quickly as possible, ”said Fauci, director of the National Institute of Allergy and Infectious Diseases.
“Because herd immunity is still somewhat elusive, we made a projection of what it probably would be. I’ve said it several times, between 70% and 85%, but we don’t know for sure. So rather than fixate on this, why not just say to get as many people vaccinated as possible as quickly as possible, ”Fauci said. “And with each passing day now, with over 2 million doses administered to people, we are getting closer and closer to controlling this pandemic.
The latest findings from American Red Cross antibody tests in unvaccinated donors reflect more general data.
According to a recent report from the Pew Research Center, 1 in 4 Americans report having had Covid-19. One in three Hispanic adults report having contracted the virus, and young adults are more likely than older adults to say they carry the virus. The results suggest that the pandemic has affected most Americans.
In the survey, 67% say they know someone who has been hospitalized or who died from the virus. This response was passed on to the majority across all demographic groups, the report notes.
There have been around 29.5 million reported cases of Covid-19 in the United States, according to data from Johns Hopkins University, representing around 9% of the population. But experts believe the actual number of cases is much higher, which matches the findings of the American Red Cross.
The U.S. Centers for Disease Control and Prevention estimates there were more than 83 million cases at the end of December, meaning more than a quarter of the population would have been infected by the end of 2020.