While cases of Omicron have waned in recent weeks, the number of Americans who have gained immunity from the COVID variant has skyrocketed.

Data from the Centers for Disease Control and Prevention back in late January indicated that the Omicron variant made up 99.9% of all COVID cases as the strain of the highly contagious virus spread across the U.S. and much of the world.

Due to the high infection rate of Omicron, a model from the Institute for Health Metrics and Evaluation estimated that 73% of Americans now have immunity to the strain, which could rise to a staggering 80% of the population by mid-March, the Associated Press reported.

This immunity is key as it would give millions of people protection to fight off the Omicron strain if they contracted it again, or another variant of similarity, shortening illnesses and reducing the next wave of the virus should one arise.

“I am optimistic even if we have a surge in summer, cases will go up, but hospitalizations and deaths will not,” Ali Mokdad, a professor of health metrics sciences at the University of Washington in Seattle, told the AP.

Researchers at Johns Hopkins University Bloomberg School of Public Health also estimate that by the time the Omicron wave has ended, three out of four people in the U.S. will have been infected with the variant, the AP reported.

“We know it’s a huge proportion of the population,” Shaun Truelove, an epidemiologist and disease modeler at Johns Hopkins, told the AP. “This varies a lot by location, and in some areas we expect the number infected to be closer to one in two.”

Vaccines and boosters are also aiding in the fight for immunity as CDC data show that 64.5% of the eligible population has been fully vaccinated and 43% of Americans have received a booster shot.

However, more than 136,000 Americans are becoming infected with the virus daily, and more than 3,000 people in the U.S. are dying from COVID-19 each day, according to data from Johns Hopkins University.

Some experts have also warned that Omicron may not be the last variant that the U.S. will see, and the next strain of the virus could be more severe.

World Health Organization leader Dr. Tedros Adhanom Ghebreyesus said last month that “it is dangerous to assume that Omicron will be the last variant, or that we are in the endgame.