DENVER — As you rub your neck from the public-health whiplash that occurred this week when federal officials recommended that many people vaccinated against the coronavirus go back to wearing masks, consider this dizzying detail:

Residents of some of the most-vaccinated counties in Colorado — the places that state officials have lauded as doing the best job in working to stop the virus — are now being urged to resume donning that most prominent of pandemic precautions. Residents of some of the least-vaccinated counties in Colorado are not.

This seemingly incongruous scenario is due to the pandemic taking yet another surprising turn in Colorado.

The new guidance from the Centers for Disease Control and Prevention recommends that people in areas with lots of new coronavirus cases resume wearing masks when around others indoors. The guidance puts the threshold for mask-wearing at 50 new cases per every 100,000 people over the previous week or at a test-positivity rate of at least 8%.

A month or two ago in Colorado, a county’s vaccination rate was a somewhat reliable predictor of what its coronavirus case rate would be. Counties with higher vaccination rates generally had lower case rates, and counties being hit hard with surges of infections — Mesa County was a frequently cited example — often had lower vaccination rates.

Read more at ColoradoSun.com.