Americans once again should wear masks indoors in schools and areas with high rates of COVID — even those who are fully vaccinated, according to recommendations Tuesday from the U.S. Centers for Disease Control and Prevention.

But the new guidance, which targets counties of “substantial or high transmission,” unleashed plenty of questions.

Chief among them: Will anybody listen?

For now, requiring masks will be left up to businesses, universities and others — rather than state or county officials, said Linda Vail, Ingham County health officer.

“What’s the likelihood that anybody’s going to tolerate any kind of epidemic orders right now?” she asked.

This week, 11 Michigan counties were deemed as counties of “substantial or high” transmission: Gogebic, Iron and Dickinson in the western Upper Peninsula; Mason, Kalkaska and Alpena in northern Michigan; and Van Buren, Cass, Branch and Hillsdale on Michigan’s southern edge. Sixteen others scattered throughout the Upper Peninsula and northern Michigan were listed as having “low transmission.”

The CDC’s latest action reversed earlier decisions, and it complicated already difficult decisions for businesses, governments, public health officials and school districts as the second half of summer gives way to back-to-school and cooling temperatures that will drive people back inside.

The reversal comes as COVID cases have increased more than 100 percent nationwide in the past 14 days, driven in large part by the contagious Delta variant and plateauing vaccination efforts.

Michigan cases remain relatively low compared to other states, but they as well have crept upward in recent weeks. On Tuesday, Michigan added 1,762 cases for the previous four days, an average of 440 per day.

Ten days ago, the state was averaging about 290 cases per day — still far below the third wave this spring when the average daily rates peaked at 7,014 cases but a worrisome trend to health officials.

“It seems that, with letting our guard down and not reaching the level that we want in vaccination, we’re at this point again” of indoor masks, said Jimena Loveluck, health officer at the Washtenaw County health department.

“It is frustrating, but at the same time, these are the kinds of things that in public health, we have to respond to in order to protect our community members,” she said.

But she, too, said she doesn’t expect state or local orders to require masks just yet.

Will masks be required?

Michigan lifted its mask mandate and remaining pandemic rules in June, and any return to them will face the groundswell of opposition to such requirements 16 months into a pandemic.

On Tuesday, Gov. Gretchen Whitmer wore a face mask at an indoor press conference on affordable housing in Detroit.

Whitmer said Dr. Joneigh Khaldun, chief medical executive, recommended that the governor return to mask-wearing indoors and in groups.

However, Whitmer said she doesn’t expect to announce any other mandate.

“I do not anticipate another pandemic order, not in the near future and maybe not ever,” Whitmer told reporters. “The best way to stay safe is to get vaccinated. We’re really strongly encouraging everyone to do just that.”

Local health officials share the same sentiment.

“It really comes down to, right now, a citizen’s decision whether or not they’re going to wear a mask,” said Ann Hepfer, health officer for Bay and Tuscola counties at the tip of Michigan’s Thumb.

Meantime, the health department will step up assistance to make sure local employers and others have adequate masks and other resources.

“We want to stay open, right? And we know that masks and social distancing works,” she said.

Hepfer finds truth in the old adage that “you get more with honey” than sour lemons or vinegar — something she said is especially true in the current climate.

“If you could encourage people and educate them, they will make their own decisions,” she said.

At the Michigan Restaurant and Lodging Association, Jason Winslow agreed, saying such decisions must remain local, based on community need and demand.

What works for Ann Arbor may not work in a northern Michigan city — a statement truer today than it was, say, in the middle of the pandemic, said Winslow, the association’s president and CEO.

“This industry interacts with the public — whether you’re on the restaurant or the lodging side — so tremendously every single day that they need to be responsive to the general sense of that community,” he said.

Sweeping mandates make him “genuinely concerned,” about the safety of the industry’s workers.

“I don’t know whether the public is going to be — this far removed from any restrictions and regulations COVID — (willing) to go back,” he said.

What does this mean for schools?

It’s not clear, but it likely will vary from district to district.

Across the state, local health and school officials are now hammering out back-to-school plans. A possible mask mandate tops the list of the toughest calls to make, said Karen Senkus, health officer for the Chippewa County health department on the eastern tip of the Upper Peninsula.

“It is really tough. I get asked that question every day,” about whether there will be a mandate, she said.

Earlier this week, they were still wrestling with it, as she and others did a daily review of hospitalizations, case rates and other data in the area, Senkus said.

The latest guidance from Michigan health officials makes it clear that local officials are in charge for the time-being, likely leading to a patchwork of policies if cases continue to rise.

The two-page guidance, issued June 25, reads, in part, “the number and intensity of prevention strategies can be adjusted based on the level of COVID-19 transmission in the community.”

In Chippewa County, nearly every recent COVID case has been among the adults, Senkus noted. Still, that could change quickly. School policies over things like masking likely will change quickly, too.

“We really need to be flexible this year,” she said.

How does masking affect vaccines?

Vaccinations remain the key for thwarting the virus, health officials say.

But vaccine rates have stalled — as of Tuesday, just under 60 percent of Michiganders had had a first dose, far short of the state’s 70 percent goal.

At least two Michigan health care giants — Henry Ford and Trinity Health — now require vaccinations.

Meanwhile, the U.S. Department of Veterans Affairs announced this week that many of its front line workers will be required to be vaccinated, and the the Department of Justice this month released an 18-page opinion saying federal law doesn’t prohibit employers from such requirements.

As masking and other mitigating measures fall by the wayside, and the pandemic is fueled by Delta and other variants of concern, vaccinations will be even more critical, said Loveluck, the health officer at Washtenaw County.

Loveluck said she’s not requiring her staff to be vaccinated “at this time.” Most already are, she said.

But she predicts that other employers may begin requiring vaccines or mandating more testing among employees who refuse.

“This is one of the best ways to help everyone be able to get back to life as it was before COVID,” Loveluck said of the vaccines.