Herd immunity is possible when enough people have contracted and become immune to a virus, providing community-wide protection by limiting the number of people who can spread it. And while the strategy is considered controversial and even downright dangerous by many public health experts, it is also reportedly gaining momentum in the White House.
According to a report by the Washington Post, herd immunity is a strategy being pushed by Dr. Scott Atlas — a neuroradiologist with no background in infectious diseases or epidemiology who recently joined the White House as a pandemic adviser.
Atlas denied that he had encouraged the White House to adopt a herd immunity strategy, and on Wednesday White House coronavirus task force coordinator Dr. Deborah Birx and top infectious disease expert Dr. Anthony Fauci dismissed the idea that herd immunity was under consideration. An administration official, however, told CNN that the policies being promoted by Atlas are indeed akin to a herd immunity approach.
Ordinarily, herd immunity would be acquired through a majority of the population being vaccinated — not through immunity acquired by natural infection.
“Normally, when we talk about herd immunity, we talk about how much of the population needs to be vaccinated,” World Health Organization (WHO) COVID-19 technical lead Dr. Maria Van Kerkhove said on Aug. 27. “If we think about herd immunity in a natural sense of just letting a virus run, it’s very dangerous because you would need a lot of people to be infected.”
It’s still uncertain what percentage of a population would need to be immune to the virus in order to attain herd immunity. According to Johns Hopkins University, in general, the answer is 70 to 90 percent of a population, depending on how contagious the infection is. But a model published last month in the magazine Science found that the threshold needed for coronavirus herd immunity could be as low as 43 percent.
Proponents of herd immunity have looked to emulate Sweden’s more hands-off approach; unlike most countries in Europe, the Nordic country opted out of a nationwide lockdown and kept most businesses open.
But Sweden’s strategy didn’t entail a total return to normalcy. The Swedish government implemented a ban on gatherings of 50 people or more, and many Swedes voluntarily followed social distancing guidelines.
Former FDA Commissioner Scott Gottlieb noted in an op-ed published on Aug. 30 that in addition to being much larger than Sweden (a country with a population the same size as North Carolina’s), the U.S. has a high rate of citizens with preexisting conditions, which can lead to a higher rate of COVID-19 complications; about 10 percent of Americans have diabetes, and 40 percent are considered obese.
Moreover, Sweden’s pursuit of natural herd immunity doesn’t appear to be working. A study released in June by the country’s Health Agency showed that only 6 percent of Swedes had developed antibodies to the coronavirus — though a recent study from Sweden’s Karolinska Institute and Karolinska University Hospital suggests that immunity in Sweden may be higher than antibody tests indicate.
The role of antibodies and how much of an impact they have on long-term immunity is still questionable. A U.K. study, which had not yet been peer-reviewed, found that antibodies may start to decline 20 to 30 days after the onset of COVID-19 symptoms. And a Chinese study found that antibody levels in patients who had recovered from COVID-19 fell sharply within two to three months after infection.
Falling antibody counts may not necessarily mean waning immunity; other immune responses such as T-cells could also affect how long immunity lasts. But the case for natural herd immunity is made even more improbable by reports of coronavirus reinfections in Hong Kong, Europe and the U.S. If natural immunity is as short-lived as a few months, that wouldn’t be stable enough to provide community or nationwide protection.
Yahoo News Medical Correspondent Dr. Dara Kass says waiting to reach the minimal number of infections needed for natural herd immunity to work would not only take longer than waiting for a vaccine (which could come before the end of the year, according to the CDC) but would also likely cost more lives. Even if only 40 percent of the U.S. population needed to contract and recover from COVID-19 to reach natural herd immunity, Kass argues, that would mean another 126 million more Americans would still need to be infected.
“It’s taken us six months to get to 6 million infections,” Kass says. “What if we just said, let’s live life like normal? Let’s not wear masks, let’s not socially distance, let’s ride the subways and go to work. How fast could we get to 126 million infections? One year? Two years? Three years? We don’t know. But what we know is, the faster we infect people, the more people will die.”
“We’ve seen so far 185,000 Americans die of this coronavirus with 6 million people infected,” Kass continues. “If we want to intentionally infect another 126 million Americans, that means that over 1 million more Americans would die of this virus before we infected enough people to get to any possible natural herd immunity.”
According to a Gallup poll conducted in late July, 35 percent of Americans said they would not get a coronavirus vaccine even if it were FDA-approved and available to them at no cost. But Kass says a vaccine will likely be the key to any workable herd immunity strategy.
“The bottom line is, will herd immunity be the answer to this coronavirus pandemic? And the answer will be yes — but not natural herd immunity. We will get to herd immunity hopefully with the development of a safe, effective vaccine,” Kass says.
“Until we have a safe and effective vaccine that is available to the hundreds of millions of Americans that still need to be exposed and recovered from this virus, we just need to continue to do the hard work, which means wear a mask, be socially distanced from people you don’t know, wash your hands multiple times a day and listen to the science.”
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