COVID-19 updates: 2 cases of omicron variant confirmed in Canada, officials say

Denver area hospitals are 95% full, Denver Health CEO Robin Wittenstein warned at a Tuesday news conference.

"Emergency rooms are routinely diverting patients because they simply don't have the capacity to take care of people who need help," Wittenstein said.

Eighty-three percent of hospitalized COVID-19 patients in Colorado are unvaccinated, said Bob McDonald, executive director of Denver's Department of Public Health and Environment.

"To suggest that the vaccines don't work... that's like suggesting seatbelts don't work," McDonald said.

Denver is implementing an indoor mask mandate unless businesses choose to require proof of vaccination.

-ABC News' Zachary Ferber

The Biden administration is asking a federal court to immediately reinstate a nationwide vaccine mandate for large businesses, arguing that the COVID-19 threat to unvaccinated workers is “ongoing and overwhelming.”

The mandate was supposed to go into effect Jan. 4. It was put on hold by another federal court that insisted the Labor Department’s Occupational Safety and Health Administration didn’t have the legal authority to impose such a requirement on private businesses.

In the new court filing to the 6th Circuit Court of Appeals, the Biden administration responded, “Congress charged OSHA with addressing grave dangers in the workplace, without any carve-out for viruses or dangers that also happen to exist outside the workplace."

“Delaying this standard would endanger many thousands of people and would likely cost many lives per day,” the lawyers wrote, adding that there was “extensive evidence of ‘workplace transmission.’”

-ABC News' Anne Flaherty

In September, unvaccinated people had a 5.8 times greater risk of testing positive for COVID-19 compared to vaccinated individuals, according to federal data pulled from 24 states and jurisdictions that has been published on the CDC website.

The unvaccinated are 14 times more likely to die from COVID-19, according to the CDC.

At Monday's White House COVID-19 briefing, CDC Director Rochelle Walensky said unvaccinated adults are nine times more likely to be hospitalized for the virus compared to vaccinated adults.

-ABC News' Arielle Mitropoulos

The Michigan Hospital Association is warning of strained health systems as COVID-19 surges across the state.

Michigan is fast approaching its highest number of COVID-19 hospitalizations since the pandemic began, with more than 3,900 patients currently receiving care, according to state data. The vast majority of patients in the ICU and on ventilators are unvaccinated.

"Most hospitals throughout the state have more patients in their emergency departments than they do available rooms and staff to care for them," officials wrote in a statement on Monday. "This results in long wait times, patients being placed in hallways or conference rooms, and diverting patients away from a hospital because there is no physical room or medical staff available to accept more patients."

"We are extremely concerned because our best predictions are that COVID-19 patients will continue to increase during the weeks ahead as we enter the yearly flu season," they said.

-ABC News' Arielle Mitropoulos