'Herd immunity' gives way to 'good enough' as Biden sets new benchmark for vaccines - ABC News

Since the pandemic began, Americans have embraced the idea that the virus would one day evaporate, either because enough people became infected with the virus or received a vaccine.

That collective, or "herd," immunity would block the virus from transmitting to new people, eradicating the threat.

The idea was so alluring that some top advisers to President Donald Trump called for allowing younger people to get sick with the virus so it would go away sooner and businesses could reopen without restrictions.

By January, five days after taking office, Biden said he was "confident that by summer we're going to be well on our way to heading toward herd immunity." And by March, Biden said herd immunity was a prerequisite to giving up masks.

"We've got to reach the point where we have herd immunity -- meaning where we have a vast majority of the American people have been vaccinated -- before we can stop wearing these," Biden said this spring, holding up his mask.

Scientists said the concept of herd immunity has always been nuanced and a difficult threshold to pinpoint.

Although often taken to mean total eradication of the virus, herd immunity can also be defined around more manageable goals, such as dramatically slowing down transmission.

In a private phone call Tuesday between the nation's governors and the White House, Fauci tried to steer state officials away from any estimate because he said no one knows what the magic number would be.

So our goal is just get as many people as you can possibly get vaccinated, and don't get hung up on this elusive concept of a number that nobody really knows what that number is," Fauci told the governors.

According to a senior administration official, Biden's new benchmark was less about doing away with any notion of herd immunity and more about setting "a collective goal for the country" now that the president's first 100 days in office had passed.

Frieden said new, potentially more dangerous variants of the virus developing overseas remain the wildcard.

"I understand that people want clarity," Frieden said