Trump’s wrong. 15% ‘herd immunity’ is not on par with strength of a vaccine

Reviewed by Emily Henderson, B.Sc.Dec 15 2020

During a Dec. 8 press conference about Operation Warp Speed, President Donald Trump likened the spread of the coronavirus throughout the population — which experts agree bestows some immunity on the people who became ill — to having a COVID-19 vaccine.

"You develop immunity over a period of time, and I hear we're close to 15%. I'm hearing that, and that is terrific. That's a very powerful vaccine in itself," said Trump, who was responding to a reporter's question about what his message to the American people was as the holidays approach and levels of COVID cases in the U.S. continue to rise.

It wasn't the first time Trump had given credence to the idea that if enough people in a population gain immunity to a disease by being exposed to it, the illness won't be able to spread through the remainder of the population — a concept known as "herd immunity."

However, experts have warned that attempting to achieve herd immunity naturally, by allowing people to get sick with COVID-19, could result in more than a million deaths and potentially long-term health problems for many. A better way to achieve protection across the population, experts say, is through widespread vaccination.

So, we thought it was important to check whether 15% is anywhere close to the herd immunity threshold, and whether this level of natural immunity could be considered "as powerful as a vaccine."

15% is nowhere close

The White House did not respond to our request for more information about the comment or about Trump's 15% figure.

It may be derived from a Nov. 25 Centers for Disease Control and Prevention report using mathematical models to estimate that 53 million Americans — about 16% of the population — have likely been infected with COVID-19. Those models took into consideration the nation's number of confirmed cases, and then used existing data to calculate estimates of the number of people who had COVID-19 but didn't seek medical attention, weren't able to access a COVID-19 test, received a false-negative test result or were asymptomatic and unaware they had COVID-19.

It's important to note this estimate is based on data from February through September — and it’s now mid-December, so the share of Americans who have been infected with the coronavirus would likely be much higher. For instance, an independent data scientist, Youyang Gu, estimated that 17.5% of Americans have had COVID-19 as of Nov. 30. His estimate is published on his website, COVID Projections.

Experts have said that a 15% infection rate among Americans is nowhere close to the threshold needed to reach herd immunity against COVID.

"To get to herd immunity, an estimated 60-80% of people need to have immunity (either through natural infection or through the vaccine)," Dr. Leana Wen, an emergency physician and visiting professor at George Washington University, wrote in an email. "We are a very long way off from that."

Also, Wen said, scientists still don't know enough about how effective natural immunity is in defending against COVID-19. It appears that once someone has had COVID-19 and recovered, the antibodies their body produced can protect them for at least several months. But, there have also been reports of COVID-19 re-infection.

That's why medical experts urge everyone to get vaccinated, whether they have had COVID-19 or not.

Dr. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, recently set the saturation level for herd immunity even higher — between 75% and 80% — in an interview with Axios.

At that point, he said, "you create an umbrella of herd immunity — that even though there is virus around, it is really almost inconsequential because it has no place to go, because almost all of the people are protected.”

Both the Pfizer and Moderna COVID-19 vaccines have shown 95% effectiveness at protecting people from developing COVID-19 in clinical trials. The Food and Drug Administration on Friday authorized Pfizer's vaccine for emergency use. This Thursday, an independent panel will consider whether to recommend that the FDA authorize the emergency use of Moderna's COVID-19 vaccine.

So, that leads to the next question: Is 15% natural immunity among the American population anywhere close to a "powerful vaccine," as Trump alleges?

No, said the experts. And there's nothing "terrific" about that level of infection within the community.

"Fifteen percent 'natural immunity' is nowhere close to as powerful as a vaccine," Dr. Rachel Vreeman, director of the Arnhold Institute for Global Health at the Icahn School of Medicine at Mount Sinai, wrote in an email.

Assuming that natural immunity is effective, reaching a level of 15% of the population would prevent only those individuals who have had COVID from getting sick again, said Stephen Morse, an epidemiology professor at Columbia University.

"But [it] won't do much to prevent virus spread in the community, because there are still so many susceptible people," Morse wrote in an email. Plus, 15% of the American population having had COVID-19 "has come at a high cost," Morse wrote. To achieve 15% natural immunity, more than 300,000 people in the U.S. have been sacrificed.

Our ruling

Though Trump was in the ballpark when he referenced the share of Americans who have been infected with the coronavirus, his overall point — that the natural immunity these people acquired is a powerful vaccine — does not hold up. Experts repeatedly have warned that not enough is known about the immunity people appear to gain after recovering from a COVID-19 infection to know how effective or lasting it is. And there have been reported cases of COVID re-infections.

Also, experts agree more than 70% of the U.S. population needs to be vaccinated in order to reach herd immunity. Fifteen percent is nowhere close to that threshold and should not be considered as effective as a COVID-19 vaccine. Moreover, that 15% statistic brought with it hundreds of thousands of deaths.

We rate this claim False.