More than 70% of Americans now have immunity against the omicron variant, according to a new model by the Institute for Health Metrics and Evaluation (IHME)—a level of protection several health experts say will likely help relieve overwhelmed hospitals and blunt the impact of future surges.

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Americans' immunity against omicron

For the model, IMHE researchers analyzed several factors, including the number of infections, vaccine coverage, booster uptake, and more to calculate Americans' current level of immunity against omicron.

By the beginning of February, IMHE estimated that 75% of Americans had received at least one dose of a Covid-19 vaccine while 66% had been fully vaccinated. Around half of those who are fully vaccinated have also received booster doses. In addition, around 130,000 Americans are being infected by the coronavirus each day.

Overall, IHME estimates that 73% of Americans are now immune to the omicron variant—and this number could rise to 80% by mid-March.

Similarly, scientists from the Johns Hopkins Bloomberg School of Public Health estimate that around three out of four Americans will have been infected by the omicron variant by the end of the current surge.

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"We know it's a huge proportion of the population," said Shuan Truelove, an epidemiologist and disease modeler at Johns Hopkins. However, Truelove added that infection rates "var[y] a lot by location, and in some areas we expect the number infected to be closer to one in two."

Will endemicity soon be possible?

This increase in immunity among the American population will likely help prevent or shorten new infections, as well as reduce the overall amount of viral transmission, health experts said. Hospitals will also likely see reduced patient loads going forward, and any future waves should be less severe.

"We have changed," said Ali Mokdad, a professor of health metrics sciences at the University of Washington. "We have been exposed to this virus and we know how to deal with it."

"I am optimistic even if we have surge in summer, cases will go up, but hospitalizations and death will not," Mokdad added.

However, the level of immunity will vary depending on the area, with Americans who are vaccinated and boosted having the most immunity. Some people will also remain vulnerable to the coronavirus because they were neither vaccinated nor previously infected.

According to the Associated Press, it is estimated that 80 million Americans, or around 26% of the total population, still do not have any immunity against the coronavirus, whether through vaccination or infection. "The 26% who could still get omicron right now have to be very careful," Mokdad said.

In addition, Andrew Pekosz, a virus researcher at Johns Hopkins, said he is concerned that some people, particularly unvaccinated people who were infected with omicron, have a false sense of security about their immunity. "In an ideal world, unvaccinated individuals infected with omicron would be lining up for a vaccine shot," he said.

Overall, Mokdad said the increased immunity through vaccination and infections has allowed the United States to reach "a much better position for the coming months, but with waning immunity we shouldn't take it for granted." (Johnson, Associated Press, 2/17; Folmar, The Hill, 2/18; IHME Covid-19 projection data, accessed 2/21)