A herd immunity strategy to fight the pandemic can be "dangerous," experts say. We explain why

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(CNN) -

After months of efforts to limit the spread of the new coronavirus in the United States, herd immunity has become a controversial topic.

Dr. Scott Atlas, a member of the White House task force on coronavirus, responded on Monday to a report claiming that he is an advocate of a "herd immunity" strategy to combat COVID-19.

"I have never advocated for that strategy," Atlas told a news conference in Florida.

Such an approach, similar to the one followed in Sweden, would mean that many people across the country would have to get sick with Covid-19 to develop natural immunity in all communities.

As the virus spreads and makes people sick, many could die in the process.

Atlas explicitly denied that it is promoting a herd immunity strategy, but a government official told CNN that all the policies that Atlas has promoted are in line with a herd immunity strategy.

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Atlas has rejected the need for widespread community testing, arguing that the Trump administration should focus almost exclusively on protecting and screening elderly populations while pushing for the rest of the economy to return to normal, this official said.

"Everything he says and does points to herd immunity," said the senior administration official.

About 2 million Americans could die in an effort to achieve herd immunity to the coronavirus, CNN emergency physician and medical analyst Dr. Leana Wen said Monday.

Wen told CNN's Brianna Keilar that she has "great concerns" about a herd immunity approach and that it is still unknown how long immunity to COVID-19 might last.

"If we are waiting until 60% to 80% of people have it, we are talking about more than 200 million Americans getting infected, and with a mortality rate of 1%, let's say, that's 2 million Americans those who would die in this effort to try to gain herd immunity, "Wen said.

"Those are preventable deaths of our loved ones that we simply cannot allow to happen under our supervision."

Maria Van Kerkhove, World Health Organization (WHO) technical lead for the coronavirus response, said, during a press conference in Geneva last week, that "herd immunity" is typically discussed in the context of vaccines, not as a response to a pandemic.

"Normally when we talk about herd immunity, we talk about how much population needs to be vaccinated to have immunity to the virus, to the pathogen, so that transmission no longer occurs or it is very difficult for a virus or pathogen to be transmitted between people," said Van Kerkhove.

"If we think of herd immunity, in the natural sense of letting a virus run, it is very dangerous," he said.

"That means that many people are infected, many people will need hospitalizations and many people will die."

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Sweden's "herd immunity" efforts

Herd immunity refers to a specific threshold of protection that a certain population or community must have against an infectious disease to keep it at bay, and that protection can come from previous infections or from vaccination, he told CNN on Monday. Dr. Amesh Adalja, principal investigator at the Johns Hopkins University Center for Health Security.

“If a herd immunity threshold has been crossed, it is very difficult for an infectious disease to find new people to infect and maintain transmission in that community,” Adalja said, adding that when it comes to Sweden, “it doesn't seem like the herd immunity threshold was crossed there, as far as we know. '

Unlike most countries, Sweden did not go into quarantine when the pandemic swept across Europe in early spring.

Instead, the emphasis was on personal responsibility, and most bars, schools, restaurants, and lounges remained open.

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Despite the more relaxed approach, only 7.3% of people in Stockholm had developed the antibodies needed to fight the disease, by the end of April, well below the 70-90% needed for herd immunity.

Now the country has more than 5,800 deaths from covid-19, which corresponds to approximately 576.38 deaths per million inhabitants.

So far, the most recent death from covid-19 was registered on August 23.

The number of deaths per million in the country is much higher than that of some of its closest neighbors, with similar low population densities, such as Denmark, at 107.73;

Finland, with 60.46;

Norway, with 48.7, or Estonia, with 48.25.

"When the majority of the population is immune to an infectious disease, this provides indirect protection (herd immunity) to those who are not immune to the disease by acting as a bulwark against new waves of infections from the population," wrote Eric Orlowski of the University College London, and Dr. David Goldsmith, a retired London-based physician, in a commentary published in the Journal of the Royal Society of Medicine in mid-August.

“It is likely that part of this difference between Scandinavians in mortality results is also due to the fact that the most vulnerable Swedes were not protected from viral infections (between 40% and 50% of their cases have occurred in the resident population nursing homes), ”Orlowski and Goldsmith wrote.

"But as with other aspects of this unprecedented crisis, it takes more time to understand the many lasting impacts."

Much of the criticism surrounding Sweden's response has focused on the high death rates in nursing homes.

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"It is not obvious how to completely isolate people who are at risk of severe illness from those who generally have mild illness," Adalja said.

"The biggest problem I have with the Swedish approach is that if you're going to do that, if we're really going to try to do herd immunity, you really need to strengthen the nursing homes and you really need to do some testing, tracking and isolating," he said. .

"If herd immunity doesn't include testing, tracking and isolation, then it will be very difficult to protect vulnerable populations."

Sweden's chief epidemiologist Anders Tegnell admitted in June that the country's Public Health Agency "did not know there would be great potential for the disease to spread in nursing homes, with so many deaths."

Tegell told the Swedish newspaper Dagens Nyheter: "There are things we could have done better, but overall I think Sweden has chosen the right path."

A senior World Health Organization official praised Sweden's response to the coronavirus pandemic on Monday, saying its approach has been poorly characterized.

Dr Mike Ryan, executive director of the WHO Health Emergencies Program, said "there is a misunderstanding" that Sweden has not implemented control measures.

"It has tried to depend on individuals and communities to comply with the advice of the Government and it has tried to avoid imposing mandatory confinements, mandatory separation of individuals," said Ryan, during a press conference in Geneva, adding that this is based on historically very high levels of trust between the Swedish government and its people.

"In Sweden Anders Tegnell and the team have done a good job," said Ryan.

“That is the way the Swedish people and the Swedish Government interact.

That is the social contract in Sweden, ”he said.

"No one has come out of this pandemic with a perfect strategy."

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"Instead of pushing for herd immunity, the United States should redouble" its efforts

Dr. Scott Gottlieb, a former US Food and Drug Administration (FDA) commissioner, wrote an op-ed for The Wall Street Journal on Sunday opposing the US idea. following the model of Sweden.

“Initially, Swedish government officials tried to let the virus spread largely unchallenged among the general population while taking steps to protect older people.

The Swedish view was that the country could achieve herd immunity without jeopardizing the economy.

But keeping Sweden as an enlightened model misinterprets important parts of their experience, ”Gottlieb wrote in the op-ed.

'Many Swedes withdrew from their normal activities to protect themselves from infection anyway, even the youngest and middle-aged people.

The country experienced 5,821 COVID deaths in a population the size of North Carolina.

And Sweden is well below herd immunity, even as the country's economic recovery is among the worst in its region, ”Gottlieb wrote.

"Facing a dangerous pandemic requires containing the spread where reasonably possible."

He went on to point out that wearing face masks, testing for Covid-19 and tracking the contacts of people who have it are still helpful.

"Sweden's attempt to create 'herd immunity' has been woefully unsuccessful and is definitely not a strategy that we should try to replicate in the United States," said Dr. Howard Koh, former Deputy Secretary for Health to President Obama, and Harvard Professor of TH Chan School of Public Health, in an email to CNN, this Monday.

"What's more, pushing for 'herd immunity' now would completely change the months of work the United States has done so far in efforts to control the virus," Koh said.

"Rather than push for herd immunity, the United States should redouble the public health tools at our disposal, including the use of universal masks, widespread testing and contract tracking, until a more effective vaccine and therapies are available."

- CNN's Pamela Kirkland, Jeremy Diamond, Lauren Mascarenhas, Hilary McGann, Emma Reynolds and Vasco Cotovio contributed to this report.

covid-19 herd immunity