The state health department reported 4,867 new confirmed cases of the coronavirus and 108 deaths related to COVID-19 on Thursday.
That pushes Michigan's pandemic total number of confirmed cases of the virus to 809,591, with 17,139 deaths.
The Ottawa County health department reported 48 new cases of the virus and one death related to COVID-19 on Thursday. The county's pandemic total number of cases rises to 29,499, with a seven-day average number of new cases at 183 per day over the past week.
Ottawa County's pandemic death toll is now 377.
Muskegon County's pandemic total number of confirmed cases of the virus is now 13,150, with 317 deaths related to COVID-19.
How long does protection from COVID-19 vaccines last?
By CANDICE CHOI Associated Press
How long does protection from COVID-19 vaccines last?
Experts don't know yet because they're still studying vaccinated people to see when protection might wear off. How well the vaccines work against emerging variants will also determine if, when and how often additional shots might be needed.
"We only have information for as long as the vaccines have been studied," said Deborah Fuller, a vaccine researcher at the University of Washington. "We have to study the vaccinated population and start to see, at what point do people become vulnerable again to the virus?"
So far, Pfizer's ongoing trial indicates the company's two-dose vaccine remains highly effective for at least six months, and likely longer. People who got Moderna's vaccine also still had notable levels of virus-fighting antibodies six months after the second required shot.
Antibodies also don't tell the whole story. To fight off intruders like viruses, our immune systems also have another line of defense called B and T cells, some of which can hang around long after antibody levels dwindle. If they encounter the same virus in the future, those battle-tested cells could potentially spring into action more quickly.
Even if they don't prevent illness entirely, they could help blunt its severity. But exactly what role such "memory" cells might play with the coronavirus -- and for how long -- isn't yet known.
While the current COVID-19 vaccines will likely last for at least about a year, they probably won't offer lifelong protection, as with measles shots, said Dr. Kathleen Neuzil, a vaccine expert at the University of Maryland School of Medicine.
"It's going to be somewhere in the middle of that very wide range," she said.
Variants are another reason we might need an additional shot.
The current vaccines are designed to work against a particular spike protein on the coronavirus, said Mehul Suthar of the Emory Vaccine Center. If the virus mutates enough over time, vaccines might need to be updated to boost their effectiveness.
So far, the vaccines appear protective against the notable variants that have emerged, though somewhat less so on the one first detected in South Africa.
If it turns out we need another shot, a single dose could extend protection of the current shots or contain vaccination for one or more variants.
The need for follow-up shots will also depend partly on the success of the vaccination push globally, and tamping down transmission of the virus and emerging variants.
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COVID hospitalizations tumble among US senior citizens
By MATTHEW PERRONE and CARLA K. JOHNSON Associated Press
COVID-19 hospitalizations among older Americans have plunged 80 percent since the start of the year, dramatic proof the vaccination campaign is working. Now the trick is to get more of the nation's younger people to roll up their sleeves.
The drop-off in severe cases among people 65 and older is so dramatic that the hospitalization rate among this highly vaccinated group is now down to around the level of the next-youngest category, Americans 50 to 64.
That slide is especially encouraging because senior citizens have accounted for about 8 out of 10 deaths from COVID-19 since the virus hit the United States.
Overall, COVID-19 deaths in the U.S. have plummeted to about 700 per day on average, compared with a peak of over 3,400 in mid-January. All told, the scourge has killed about 570,000 Americans.
"What you're seeing there is exactly what we hoped and wanted to see: As really high rates of vaccinations happen, hospitalizations and death rates come down," said Jodie Guest, a public health researcher at Emory University.
The trends mirror what is happening in other countries with high vaccination rates, such as Israel and Britain, and stand in stark contrast to the worsening disaster in places like India and Brazil, which lag far behind in dispensing shots.
According to U.S. government statistics, hospitalizations are down 60 percent overall, but most dramatically among senior citizens, who have been eligible for shots the longest and have enthusiastically received them.
Two-thirds of American senior citizens are fully vaccinated, versus just one-third of all U.S. adults. Over 80 percent of senior citizens have gotten at least one shot, compared with just over 50% among all adults.
The hospitalization rate among those 65 and over is about 14 people per 100,000 population, the Centers for Disease Control and Prevention reported, citing a surveillance system that gathers data from over 250 hospitals in 14 states.
At the same time, however, overall demand for vaccinations in the U.S. seems to be slipping, even as shots have been thrown open to all adults across the country. The average number of doses administered per day appeared to fall in mid-April from 3.2 million to 2.9 million, according to CDC figures.
"My concern is whether the vaccine uptake will be as strong in these younger age groups," Guest said. "If it's not, we will not see the positive impact for vaccines in these younger age groups that we've seen in our older population."
Also, new virus cases in the U.S. have been stuck at worrisome levels since March, averaging more than 60,000 per day, matching numbers seen during last summer's surge. The new cases are increasingly among people in their 30s, 40s and 50s, who also make up a larger portion of hospitalizations.
In Michigan, which has been battered by a recent surge of infections, hospitalizations among people in their 50s have increased 700% since late February, outpacing all other age groups.
In Seattle's King County, hospital physicians are seeing fewer COVID-19 patients overall, fewer needing critical care and fewer needing breathing machines. These younger patients are also more likely to survive.
"Thankfully they have done quite well," said Dr. Mark Sullivan, a critical care doctor at Swedish Medical Center in Seattle. "They tend to recover a little quicker because of their youth."
With enough people vaccinated, COVID-19 cases should eventually begin to fall as the virus finds fewer and fewer people to infect. Guest and other experts say Israel appeared to reach that threshold last month after it fully vaccinated roughly 40 percent of its population of 9 million people.
But the U.S. faces challenges in conducting mass vaccinations because of its far greater size, diversity, geography and health disparities.
On Tuesday, President Joe Biden announced new federal funding for small businesses so that employees can take time off with pay to get vaccinated or recover from the shot's side effects.
The challenge will be quickly vaccinating younger Americans, who feel they are less vulnerable to the coronavirus but are mainly the ones spreading the disease.
"To really feel that we're out of the woods we've got to see a lot less cases than we're seeing now," said Dr. Jesse Goodman, a vaccine specialist at Georgetown University. "It's going to take a wider, continuing effort."
In Chicago's Cook County, where 91 percent of adults 65 and older have had at least one shot, the patients in the hospital these days are younger and do better.
"That feeling of dread is definitely eased with older patients getting vaccinated," said Dr. Tipu Puri, a kidney specialist and associate chief medical officer for clinical operations at University of Chicago Medical Center.
At some moments, there's even joy, he said. He recently stopped to help an elderly couple find the hospital's vaccination clinic. The woman was pushing her husband's wheelchair.
"Those are people you hope you won't see in the hospital," Puri said. "We're not going to see them in the emergency room or in the ICU."
He added: "This is what coming out of the pandemic feels like."
AP Health Writer Tom Murphy contributed to this story from Indianapolis. Johnson reported from Seattle.