While experts said months ago that reaching a level where so many people had either had COVID-19 or been vaccinated against the virus — thus giving them antibodies — was possible, some are now saying that herd immunity might be impossible, citing the spread of variants.
“This month, the Infectious Diseases Society of America estimated that delta had pushed the threshold for herd immunity to well over 80% and possibly close to 90%,” Bloomberg reports. “Public health officials like Anthony Fauci have drawn controversy by shifting the goalposts over the past year, increasing the number of people who need protection before hitting herd immunity. Meanwhile, vaccine hesitancy and supply issues mean most countries won’t get close to even the original numbers.”
“Will we get to herd immunity? No, very unlikely, by definition,” Greg Poland, director of the Vaccine Research Group at the Mayo Clinic in Rochester, Minnesota, told the news agency.
Poland said that herd immunity can’t be reached even with a vaccination rate of as high as 95%. “It is a neck and neck race between the development of ever more highly transmissible variants which develop the capacity to evade immunity, and immunization rates,” he said.
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.
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, has 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 last month 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.”