Herd immunity from Covid-19? Not likely. Herd resistance? Yes.

Modern Healthcare illustration

A recent report estimated that 73 percent of Americans have immunity to the coronavirus, either from being infected by it or by getting vaccinated against it. That has made some people say that the nation is approaching "herd immunity," which protects unvaccinated people by making it more difficult for the virus to circulate.

That's unlikely, experts say. But they do think the highly contagious Omicron variant has spread so widely that it provided "enough protection against the coronavirus that future spikes will likely require much less — if any — dramatic disruption to society," reports Carla K. Johnson of The Associated Press.

“Herd immunity is an elusive concept and doesn’t apply to coronavirus,” Dr. Don Milton at the University of Maryland School of Public Health told Johnson.

"Early hopes of herd immunity against the coronavirus faded for several reasons," Johnson writes. "One is that antibodies developed from available vaccines or previous infection dwindle with time. While vaccines offer strong protection against severe illness, waning antibodies mean it's still possible to get infected — even for those who are boosted."

Also, vaccination has slowed, many areas still have low vaccination and booster-shot rates, and children under 5 still aren't eligible to be vaccinated, Johnson points out.

Finally, "As long as the virus spreads, it mutates, helping the virus survive and giving rise to new variants," Johnson notes. "Those mutants, such as Omicron, can become better at evading the protection people have from vaccines or an earlier infection."

Milton told Johnson that we are moving toward “herd resistance,” in which there is enough protection that outbreaks will be smaller and not disrupt society as the previous surges.

"Many scientists believe Covid-19 will eventually become like the flu and cause seasonal outbreaks but not huge surges," Johnson reports.

Ali Mokdad, a professor of health metrics sciences at the University of Washington, calculated the 73% immunity figure at the Johnson's request. 

"I am optimistic even if we have a surge in summer, cases will go up, but hospitalizations and deaths will not,” he said.