A herd immunity strategy to fight the pandemic can be 'dangerous,' experts say. Here's why

“Everything he says and does points toward herd immunity,” the senior administration official said.

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

Wen told CNN’s Brianna Keilar that she has “huge concerns” about a herd immunity approach and much is still unknown about how long immunity to Covid-19 might last.

“If we’re waiting until 60% to 80% of people have it, we’re talking about 200 million-plus Americans getting this — and at a fatality rate of 1%, let’s say, that’s 2 million Americans who will die in this effort to try to get herd immunity,” Wen said. “Those are preventable deaths of our loved ones that we can just not let happen under our watch.”

“Normally when we talk about herd immunity, we talk about how much of the population needs to be vaccinated to have immunity to the virus, to the pathogen, so that transmission can no longer take place or it’s very difficult for a virus or a pathogen to transmit between people,” Van Kerkhove said.

“If we think about herd immunity in the natural sense of just letting a virus run, it’s very dangerous,” she said. “That means that many people are infected, many people will need hospitalizations and many people will die.”

Sweden’s ‘herd immunity’ efforts

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

“If a herd immunity threshold has been crossed, it is very difficult for an infectious disease to be able to find new people to infect and to sustain 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, from all we can tell.”

Now the country has more than 5,800 deaths from Covid-19, corresponding to about 576.38 deaths per million people. The last Covid-19 fatality was recorded on August 23.

The number of deaths per million in the country is much higher than some of its closest neighbors, with similar low population densities, namely Denmark at 107.73, Finland at 60.46, Norway at 48.7 or Estonia at 48.25.

“It is likely that some of this inter-Scandinavian difference in mortality outcomes might have also have arisen from a failure to shield the most vulnerable Swedes from viral infections (40%–50% of their cases have been in the elderly nursing home resident population),” Orlowski and Goldsmith wrote. “But as with other aspects of this unparalleled crisis, more time is needed to understand the many lasting impacts.”

Much of the criticism around Sweden’s response has focused on the high death rates in care homes.

“It’s not obvious how to completely isolate those people that are at risk for severe disease from those who generally get mild disease,” Adalja said.

But he told Swedish newspaper Dagens Nyheter: “There are things that we could have done better but in general I think that Sweden has chosen the right way.”

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

“That is the way in which Swedish people and the Swedish government interact. That is the social contract in Sweden,” he said. “Nobody has come through this pandemic with a perfect strategy.”

‘Instead of pushing for herd immunity, the U.S. must double down’

“Swedish government officials initially sought to let the virus run largely unchallenged in the general population while taking steps to protect the elderly. The Swedish view was that the country could reach herd immunity without jeopardizing the economy. But holding up Sweden as an enlightened model misreads important parts of its experience,” Gottlieb wrote in the op-ed.

“Many Swedes pulled back from normal activities to shelter themselves from infection anyway, even younger and middle-aged people. The country experienced 5,821 Covid deaths in a population the size of North Carolina. And Sweden is far short of herd immunity, even as the country’s economic recovery ranks among the worst in its region,” Gottlieb wrote in part. “Confronting a dangerous pandemic requires containing spread wherever it is reasonably possible.”

He went on to note that wearing masks, testing for Covid-19, and tracing the contacts of people who have it remain helpful.

“Sweden’s attempt to create ‘herd immunity’ has been woefully unsuccessful and is definitely not a strategy we should seek to replicate in the United States,” Dr. Howard Koh, former assistant secretary for health under President Obama and professor at the Harvard T.H. Chan School of Public Health, said in an email to CNN on Monday.

“What’s more, pushing for ‘herd immunity’ now would completely upend the months of work the U.S. has done so far in efforts to control the virus,” Koh said in part. “Instead of pushing for herd immunity, the U.S. must double down on the public health tools at our disposal — including universal mask wearing, widespread testing, and contract tracing — until a vaccine and more effective therapeutics become available.”