Colorado's arrival at the milestone of getting COVID-19 vaccine shots to 70% of people ages 70 and older opened the door for some businesses in Denver metro counties to open up to larger crowds.

Under the state's COVID-19 dial system — the set of restrictions counties must follow based on local virus spread — several Denver metro counties remain in yellow, the third least-restrictive level.

The 5-Star State Certification Program allows businesses to operate with expanded capacity if they follow stepped-up COVID-19 safety protocols, letting businesses follow restrictions that are one level lower on the dial than they otherwise would be able to without certification.

Counties across the metro area had been granted the ability to let businesses become 5-Star certified, but the state on Feb. 5 said 5-Star businesses in yellow counties could only operate at level-blue restrictions "once 70% of 70-year-olds" in the state are vaccinated with at least one dose, which was expected to happen by the end of February, according to a state public-health department news release.

On March 2, Gov. Jared Polis announced that Colorado has met the goal of vaccinating 70% of all Coloradans aged 70 and above, according to an Arapahoe County news release.

The state's COVID-19 website on March 3 listed Adams, Arapahoe, Denver, Douglas, Elbert and Weld as among the counties in yellow where 5-Star businesses can now operate in level blue restrictions.

Some counties in other areas hadn't yet been listed as able to have businesses running in blue as of that afternoon.

"Counties participating in the 5 Star Certification Program can choose whether they want their certified 5 Star businesses to operate in the blue level," said a spokesperson from the Colorado State Joint Information Center, which takes questions for the state public-health department. "We have asked eligible counties to confirm if their businesses will operate in the blue level but have not heard back from everyone yet."

In level blue, restaurants indoors are allowed up to 50% capacity or 175 people (or up to 225 using the state's social distancing space calculator), whichever is fewer. That's up from 50% capacity or 50 people (or up to 150 using the calculator), whichever is fewer, in level yellow. Other businesses see capacity expand as well. See the calculator at covid19.colorado.gov/distancing-calculator.

See a full list of which restrictions apply to which levels on the dial by clicking “level restrictions” about halfway down that page.

More counties close to Denver — including Jefferson, Park, Clear Creek and Broomfield — recently entered level blue, further loosening rules for restaurants and other businesses.

Uncertainty over 5-star relevance

Under the “dial 2.0” changes to Colorado's COVID-19 restrictions on Feb. 6, the state public-health department drastically eased the limits on incidence rates — rates of new cases — that allow counties to remain in certain levels of the dial. The arrival of the “dial 2.0” system had moved Denver metro counties down to level yellow from level orange.

The level a county qualifies for on the dial generally depends on the county's rate of new cases, its percentage of COVID-19 tests that come back positive, and whether hospitalizations are increasing, stable or declining.

The dial restrictions apply to capacity at restaurants, other businesses, indoor and outdoor events, and other settings.

The 5-Star program may soon be irrelevant in more metro counties if they're able to entirely move to level blue — unless worsening virus trends cause a county to move back up to tighter levels. That's because businesses with 5-Star certification may not operate in the next-lowest level below blue — level green, or "Protect Our Neighbors" — unless the county is formally in that level. Level green is the least-restrictive level on the dial.

It's unclear whether virus trends will allow more metro counties to move to blue soon. Despite Broomfield and Jefferson counties moving to blue, their one-week rates of new cases as of March 1 appeared to have ticked up to levels that threaten to move the counties back to level yellow.

Loss of progress possible

Although Denver metro counties sit close to qualifying for looser restrictions, trends in the state as a whole may be on a risky track if Coloradans start to have more in-person contacts and let their guard down on behaviors such as mask-wearing.

A key indicator to watch is the “effective reproduction number,” sometimes written “Re,” a measure of how rapidly COVID-19 infections are spreading. The reproduction number shows how many people each infected person will, on average, likely spread the virus to. If the number sits below 1, infections are decreasing.

Colorado's recent estimate is 0.95, reflecting the virus' spread in early February. That means the rate of new cases could soon start to increase again if the public isn't cautious.

Coloradans appeared to be having more in-person contacts in early February compared to in January, according to a Feb. 24 report by the Colorado School of Public Health. On top of that, if the more-contagious COVID-19 variant from the United Kingdom spreads rapidly in Colorado, the state could see another peak in hospital demand, the report says.

As of late February, Colorado was not seeing rapid spread of concerning variants, according to the state public-health department. But the UK variant could begin to take firmer hold by mid-March, the report says.