The Trump administration is increasingly embracing a strategy of "herd immunity" to grapple with the COVID-19 pandemic, according to multiple reports. But the controversial strategy has scientists and public health experts on edge given the limited proof that it would work for this specific outbreak and the ethical concerns which accompany it.

Tedros Adhanom Ghebreyesus, director-general of the World Health Organization (WHO), has openly lambasted the idea of using herd immunity to fight a pandemic, asserting that it's driven by a misunderstanding of the science of infectious diseases.

What is herd immunity?

To put it simply, herd immunity is the scientific theory that if enough of a population builds antibodies or gains immunity against a pathogen, they can protect those who are more vulnerable to infection. With enough immune people, the spread of a virus becomes much more containable.

The trouble is that herd immunity is a process that takes time and caution. It can't be used as a hammer against a new pathogen like the coronavirus which we're still trying to understand. Just ask Sweden, which employed a herd immunity strategy and saw disastrous results.

“Herd immunity is achieved by protecting people from a virus, not by exposing them to it,” the WHO's Tedros said in a virtual town hall last week. “Never in the history of public health has herd immunity been used as a strategy for responding to an outbreak, let alone a pandemic," adding that it would be "unethical" to rely on this strategy.

Achieving herd immunity would require a massive proportion of the population to become infected. "It varies from disease to disease. The more contagious a disease is, the greater the proportion of the population that needs to be immune to the disease to stop its spread," according to the Mayo Clinic. "For example, the measles is a highly contagious illness. It's estimated that 94% of the population must be immune to interrupt the chain of transmission."

COVID has proven quite transmissible and contagious, suggesting that herd immunity would require a higher threshold of mass immunity.

Why the U.S. is considering the herd immunity approach

The Trump administration is reportedly open to the idea of letting coronavirus run amok among younger people, who generally don't become as sick as higher-risk populations, in order to achieve herd immunity. A group of scientists endorsed the idea as a means to reopening the economy and society at large and caught the White House's attention, according to the reports.

Most of the signatories to that declaration have not been made public. But Dr. Scott Atlas, a senior scientific advisor to President Trump, is one of its major proponents. Other doctors and epidemiologists who have signed on to the declaration espouse views that are largely rejected by the scientific community, including the notion that herd immunity would only require 10% to 20% of the population to be infected.

The results of such an experiment in the midst of a pandemic the likes of which the world hasn't seen in more than 100 years could result in millions of deaths, according to critics. Current evidence, such as what's already been seen in Sweden, appears to support that thesis. And willful exposure to the coronavirus wouldn't resemble an actual, safe vaccine; it could very well just breed more chaos and suffering.