California on Thursday became the first US state to shift to an "endemic" approach to the coronavirus pandemic, moving from an emergency mindset to one that assumes people will live with the virus indefinitely.

Also on Thursday, a widely used coronavirus forecasting pandemic model estimated that 73 percent of Americans are now immune to the Omicron variant, and the University of Washington's Health Metrics and Evaluation (IHME) forecasting projected that it could go to 80 percent by mid-March.

In announcing California's new approach to COVID-19, Governor Gavin Newsom said in an interview with The Associated Press in advance of his formal announcement: "One of the fundamental lessons we've come to understand is that the disease has evolved and our understanding has to evolve in terms of how we approach it with the kind of flexibility that is required. We have to prepare for that uncertainty, we have to communicate that uncertainty and this plan is put forth with that in mind."

The coronavirus has been blamed for more 83,000 deaths in California, the nation's most populous state. Many leaders and health officials have begun to use the word "endemic" to describe the global battle with the coronavirus.

Infectious disease experts have said that the term doesn't mean COVID-19 is any less dangerous or that new variants won't raise the risk of death, but that the success of vaccines in preventing illness and death has paved the way for a new discussion on long-term priorities and safety measures.

The plan presented by Newsom includes measures to promote vaccines, stockpile medical supplies and mount an aggressive approach to disinformation.

"We're not in denial of the hell that has been the last two years," he said. But, he added, "This is not like World War II, where we can have a ticker-tape parade and announce the end."

Newsom said the plan includes pushing back against false claims and other misinformation and allows the state to "be prepared without being paranoid and more alert to what's happening around us without being anxious".

The plan sets specific goals, such as stockpiling 75 million masks, ramping up to 200,000 vaccinations and 500,000 tests a day, and adding 3,000 medical workers within three weeks in surge areas through ongoing contracts with national registry companies.

California Health Secretary Dr Mark Ghaly said, "We're gliding into normal. We're not announcing the normal. The virus will drive what we do. We're going to shift with the virus so we can keep the state as safe as possible."

The state will continue to emphasize vaccines and boosters, with expansions in school-based vaccination, including preparations to vaccinate children younger than 5 when they become eligible.

Mask requirements would be eased or tightened as required, depending on the severity and trajectory of infections, according to the plan.

Ali Mokdad, a professor of health metrics science at the University of Washington in Seattle who works on the IHME forecasting model, said, "We have changed. We have been exposed to this virus, and we know how to deal with it.''

The IHME model calculated the 73 percent figure for the AP. IHME has forecast the scope of the epidemic nationwide in every state and in several other countries and has been used by the White House and statehouses nationwide.

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