FORT SMITH, Ark – “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.”
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.