When the COVID-19 pandemic first swept the U.S. more than a year ago, Americans learned a brand-new term: Herd immunity.
The idea is simple: If enough people get a virus or a vaccine — thus building antibodies — the spread of the virus drops off precipitously.
While experts didn’t know exactly how many Americans would need antibodies to reach herd immunity, the number ranged from more than 50% to upwards of 70%. Early on in the pandemic, Dr. Anthony Fauci, the top U.S. immunologist, put the number at 60% to 70%, but in April he started upping that number, saying in an interview with CNBC News that it would be “75, 80, 85 percent.”
But now, experts are saying we may never reach herd immunity. “Instead, they are coming to the conclusion that rather than making a long-promised exit, the virus will most likely become a manageable threat that will continue to circulate in the United States for years to come, still causing hospitalizations and deaths but in much smaller numbers,” The New York Times reported on Monday.
“The virus is unlikely to go away,” Emory University evolutionary biologist Rustom Antia told the Times. “But we want to do all we can to check that it’s likely to become a mild infection.”
“We will not achieve herd immunity as a country or a state or even as a city until we have enough immunity in the population as a whole,” Lauren Ancel Meyers, the director of the Covid-19 Modeling Consortium at the University of Texas at Austin, told Times.
More than 31% of the U.S. population has been fully vaccinated, according to the Centers for Disease Control and Prevention (CDC) — including nearly 70% of Americans older than 65. But according to the Times, some 30% of Americans are hesitant to get the vaccine.
Fauci, an immunologist and director of the National Institute of Allergy and Infectious Diseases who served on former President Donald Trump’s White House Coronavirus Task Force and is now President Biden’s chief medical adviser on COVID-19, sought to explain the new pessimistic predictions.
“People were getting confused and thinking you’re never going to get the infections down until you reach this mystical level of herd immunity, whatever that number is,” he told the paper. “That’s why we stopped using herd immunity in the classic sense. I’m saying: Forget that for a second. You vaccinate enough people, the infections are going to go down.”
The Times also laid out why the estimates for herd immunity are going up.
“That is because the initial calculations were based on the contagiousness of the original version of the virus. The predominant variant now circulating in the United States, called B.1.1.7 and first identified in Britain, is about 60% more transmissible,” the paper explained. “As a result, experts now calculate the herd immunity threshold to be at least 80%. If even more contagious variants develop, or if scientists find that immunized people can still transmit the virus, the calculation will have to be revised upward again.”