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VERIFY: No, the US hasn't reached herd immunity

A recent finding by the Center for Disease Control has some people asking whether or not the U.S. reached herd immunity against COVID-19 earlier this year.

ARIZONA, USA — The Center for Disease Control recently tweeted, "Data from blood donations show Americans w/ COVID-19 antibodies increased from 20.5% to 83.3% after the rollout of #COVID19 vaccines."

The post prompted some people on Twitter to jump to the conclusion that the U.S. reached herd immunity against COVID-19.


Did the CDC find the US reached herd immunity?


  • Center's for Disease Control
  • The World Health Organization 
  • University of Arizona Epidemiologist Dr. Janet Foote



To verify what that “83%” statistic actually means in relation to herd immunity, we used three sources: The CDC, The World Health Organization, and an epidemiologist at the University of Arizona, Dr. Janet Foote.


The CDC 

The CDC’s study states that blood samples taken in May 2021 of more than a million blood donors showed “83.3% had infection-induced antibodies or vaccine-induced antibodies.”

That would appear to be good news. However, the CDC added two big caveats to this finding.

First, it noted, “…these findings from a national sample of blood donors may not be representative of the entire U.S. population…”

Second, the CDC said, "the CDC is learning more about how many people need antibodies before the population can be considered protected."


According to the World Health Organization, “The proportion of the population that must be vaccinated against COVID-19 to begin inducing herd immunity is not known. This is an important area of research and will likely vary according to the community, the vaccine, the populations prioritized for vaccination, and other factors.”

Take the measles for example. Herd immunity requires 95% of the population to be vaccinated against it. Polio requires between an 80% and 85% vaccination rate, said Dr. Janet Foote, Associate Professor at the University of Arizona.

Dr. Janet Foote 

Complicating matters, COVID-19 has variants.

“You have to realize that this virus keeps changing and our protection against it, we’re not keeping up with that change,” Foote said.

Foote said that research from Great Britain suggests antibodies from the vaccine are more effective than antibodies derived from people who get COVID-19.  

That’s why health leaders feel a sense of urgency as they try to boost vaccination rates around the country, Foote said.

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