Citing declining COVID-19 hospitalizations as the omicron coronavirus variant wanes, Colorado on Thursday deactivated its crisis standards of care that enabled hospitals and emergency medical responders to prioritize the needs of the most sick and injured and allocate staff as needed to respond to the crisis.

The announcement came as top health officials expressed cautious optimism that infections and hospitalizations will continue to decline in the coming months and possibly reach lows last seen in the summer of 2021.

Modeling by the state health department suggests that an estimated 90% of residents now are immune to infections from omicron thanks to vaccinations, public and personal precautions such as mask-wearing, and previous infections, Dr. Rachel Herlihy, the state epidemiologist, told reporters Thursday.

Herlihy warned residents not to jump to conclusions about achieving herd immunity, citing a waning of immunity over time, higher infection rates in local communities and the uncertainty surrounding future variants of the coronavirus.

Scott Bookman, the state’s incident commander for the pandemic, said he continues to recommend mask-wearing in indoor public settings even as many Colorado municipalities drop mask mandates. But he said he can see a time when indoor mask use will dwindle.

“The virus is unpredictable, and it has really been leading the show here,” Bookman said. “Our message is one of cautious optimism.”

Dr. Eric France, chief medical officer at the Colorado Department of Health and Environment, said the decision to drop the crisis standards of care was based on information provided by healthcare providers, and he, too, cited declining COVID hospitalizations and case rates in recent weeks.

Colorado enacted the protocols for hospital staffing in November and for emergency responders in January as medical facilities struggled with staffing and patient caseloads that surged because of people infected with the coronavirus.

As of Thursday, 641 people were hospitalized with COVID-19, and 413 of them, or 64%, were unvaccinated, according to the health department. That compares to more than 1,500 hospitalizations during the most recent peak in January.

Colorado’s seven-day rolling average of new cases has dropped below 1,500 per day, compared with close to 1,500 in mid-January, Herlihy said. The state’s seven-day positivity rate —- the percentage of COVID-19 tests coming back positive —- is under 7%, compared to a peak of nearly 30% in January.

More than 12,000 Colorado residents have died during the pandemic.