Is herd immunity unachievable? Researchers say 'the virus is unlikely to go away'

The goal of reaching herd immunity may be slipping away, according to some researchers, despite nearly half of all adults in the U.S. having at least one dose of the COVID vaccine.

Instead, scientists and health experts told the New York Times that the virus, with its expanding myriad of variants, will become a manageable threat that will continue to permeate the U.S. for at least the next several years, still causing hospitalizations and deaths but in much lower numbers.

Rita Antia, an evolutionary biologist at Emory University, told the Times that COVID-19 "is unlikely to go away. But we want to do all we can to check that it's likely to become a mild infection."

Vaccinations are key in keeping the virus' transmission low, but as inoculations have slowed in recent weeks, the possibility of reaching herd immunity by summer, as previously thought by some experts, seems unattainable.

As of Tuesday, the Centers for Disease Control and Prevention reported that 105.5 million Americans were fully vaccinated against COVID-19, representing 31.8% of the adult population of the U.S.

A total of 44% of all adults have had at least one dose of the shot, according to the CDC.

Dr. Anthony Fauci said in February that 70% to 85% of Americans would need to be fully vaccinated to reach herd immunity.

"As we get into the fall and winter, by the end of the year, I agree with the president completely that we will be approaching a degree of normality," Fauci told CNN on Feb. 21. "It may or may not be precisely the way it was in November of 2019, but it will be much, much better than what we're doing right now."

The U.S., however, has a way to go to reach that vaccination goal, and vaccination hesitancy isn't helping its progress and there are growing concerns about COVID-19 in hotspots like India.

Other factors can also affect herd immunity in the U.S., such as travel into other countries that don't have strong vaccination programs. In South Africa, fewer than 1% of the population have received a vaccine shot.

Vaccination and social-distancing efforts in the U.S. have made a difference, as hospitalization rates and deaths have declined. It is also believed that COVID-19 will become a seasonal virus similar to the flu.

"What we want to do at the very least is get to a point where we have just really sporadic little flare-ups," Carl Bergstrom, an evolutionary biologist at the University of Washington, told the Times. "That would be a very sensible target in this country where we have an excellent vaccine and the ability to deliver it."