As the delta variant spreads, Michigan continues to see a rising number of “breakthrough” cases, with a quarter of the most recent new infections hitting those who were fully vaccinated.

In the latest state report, nearly 2,500 breakthrough cases were reported in Michigan for the week ending Aug. 17, up from 1,900 the week before.

The number of infections among the fully vaccinated has doubled in the past four weeks, mirroring the jump in overall new cases spurred by the more virulent delta variant of the coronavirus.

But public health and hospital officials say those infections do not mean the vaccines aren’t working. They note that the infection rate remains far lower among people who are already fully vaccinated and that very few of these people end up in the hospital or dying.

“I always remind people it (the vaccine) wasn’t to prevent sniffles,” Dr. Mark Hamed, a medical officer for eight Michigan counties in the Thumb and northeast Michigan, told Bridge Michigan Thursday.

For the most ardent opponents of vaccines, breakthrough cases offer “proof” that vaccinations aren’t necessary, Hamed said. “The anti-vaxxers love that. ‘It’s a breakthrough case, it doesn’t work.’” But Hamed, who is also chair of the Michigan Academy of Family Physicians, said that’s absolutely incorrect.

Hamed said some of the vaccinated were always going to get infected. But the vaccines have helped prevent more serious illnesses, hospitalizations and death.

Statistics underscore the point. According to state and federal data:

• From the beginning of the year through Aug. 17, roughly 57,000 people entered Michigan hospitals with confirmed or suspected cases of COVID-19, data from the Centers of Disease Control and Prevention shows. The most recent state report says of those, 779 were fully vaccinated.
• Over that same period, 7,121 deaths have been tied to COVID, with 267 being people who were vaccinated, according to state data. Of those deaths, 88 percent were people 65 and older.
• The most recent infection rate for the vaccinated stands at 8 daily cases per 100,000, according to a Bridge analysis of state data. The rate for the unvaccinated is more than double, at 17 daily cases per 100,000. (As of this week, 4.6 million people in Michigan, or 55.3 percent of residents 12 and older, have been vaccinated.)
• In Michigan nursing homes, where a vast majority of residents have been vaccinated, cases are a small fraction of what they were in December. In the week ending Aug. 18, there were 73 new cases among nursing home residents, compared to 749 in the last week of December, just before the massive vaccine roll out.

The protections against serious illness from the coronavirus may be better for vaccinated individuals than even these numbers suggest. A west Michigan health system this week reported that some COVID patients who had been vaccinated were hospitalized for other reasons — injuries from a car accident, for example — but were found to be infected with COVID as a matter of routine hospital testing and are now listed among the breakthrough case hospitalizations.

“They probably got exposed (and) got infected, but they’re not showing any symptoms because their immune system has the infection already under control,” Dr. Liam Sullivan, adult infectious disease physician at Grand Rapids-based Spectrum Health, said Wednesday.

Even so, the recent rise in breakthrough cases has flummoxed some who have gotten vaccinated. There are early indications that vaccines’ efficacy has waned as the more virulent delta variant gains a toehold. Researchers are still trying to determine how much can be attributed to delta, versus a reduction in long-term effectiveness of individual vaccines. That uncertainty is part of the reason for the greater urgency to provide booster shots.

The shifts also underscore the evolving imperfections of science and the mutability of a virus that has claimed over 20,100 lives in Michigan alone.

“We have to be humble about what we do know and what we don’t know,” Tom Frieden, a former CDC director, told Bloomberg News. “There are a few things we can say definitively. One is that this is a hard question to address.”

For the vaccinated, public health officials say the increase in breakthrough cases and the rise of the delta variant shouldn’t be ignored. Hamed said he would recommend everyone, including the vaccinated, return to wearing masks when indoors away from their home.

The vaccinated “let their guard down — because we told them to,” he said, referring to the CDC’s pronouncement in May that vaccinated people could drop the wearing of masks indoors. In late July, the agency reversed that advice.

“We have to go back to mitigation measures we know worked before the vaccine,” he said.

Norm Hess, executive director of the Michigan Association of Local Public Health, said he’s not worried that a rise in breakthrough cases will make it harder to convince the vaccine hesitant to roll up their sleeves. That, he said, is already a tough sell.

He told Bridge that vaccine skeptics seem to be more concerned these days with other “issues that are front and center and louder.”

Chief among them: school mask mandates. School boards and county commissions across Michigan are facing angry residents railing against mask orders for children, even though those under 12 who are not yet eligible for vaccines.

Sullivan of Spectrum Health, in west Michigan, repeated a refrain common among doctors and public health officials Wednesday.

Vaccines, he said, “are definitely saving lives and have been overwhelmingly successful since they became available.”

They will never protect everyone from illness, said Hess.

“If people thought they were going to get a shot and never get Covid, that was never the intention,” he said. “This (the vaccine) is the most effective way to prevent suffering.”

Bridge Health reporter Robin Erb contributed to this report