Why are COVID-19 cases on the rise, with 61% of eligible Michigan residents vaccinated? – MLive.com

About 61% of the population 12 and older in Michigan have received a first dose of COVID-19 vaccine. More than 5.2 million people are at least partially vaccinated.

Yet, case numbers are on the rise. The seven-day average number of cases per day, more than 2,000, is about what it was in January or March, when fewer people were immunized.

Why is that?

The delta variant, which rose to prominence in Michigan this summer, is one reason.

Delta has this ability to infect everybody around it, said Dr. Liam Sullivan, infectious disease specialist for Spectrum Health, based in Grand Rapids. “It is very easily spread from person to person.”

Early in the pandemic, an infected person would, on average, spread the disease to two to three people, Sullivan said. With the alpha variant, delta’s predecessor, one person on average infected three to four others. With delta, a sick person transmits the illness to eight to nine people.

“All the more reason we need people who’ve not been vaccinated to get vaccinated, because the spread of this virus is never going to slow down until we get a higher degree of herd immunity in the population,” Sullivan said last week in a call with reporters.

Vaccination is another factor.

Not enough people in the state are immunized. Sullivan said the rate needs to be well over 90%.

An estimated 68% of Michigan residents have some level of protection against COVID-19, either by vaccination or previous infection, according information from the University of Michigan’s School of Public Health.

About 66.5% of people 16 and older have gotten one or more shots. Every week, the number slowly ticks upward.

In parts of the state, the numbers are much lower. In southern Michigan, for example, the rates are below 50%.

While the aim has been 70% of those 16 and older, doctors say with delta, it might need to be 80 to 90%.

Most of the people who want to be vaccinated already are vaccinated. Some are still seeking immunization. “It is kind of a slow increase, but not nearly to the amount that we want to be or need to be. But we are getting there,” said Joel Strasz, public health director in Bay County.

Strasz said cases now, though rising, are not increasing as steeply as they were earlier in the pandemic.

From Sept. 3 to Sept. 10, the seven-day average of daily, reported cases increased about 5%.

On March 17, the average was about what it is now. It had jumped from about 64% on March 10.

In January, cases were on the decline. They fell from about 2,800 early in the month to about 1,600 new, reported daily cases at the end of the month.

Vaccinations began in December and picked up speed in February and March. More vaccinations were reported in April than any other month. They have since slowed.

Cases plateaued too high in January, said Linda Vail, health officer in Ingham County. “And that means we are way too high right now as well.”

From March to mid-May, cases spiked dramatically. They dropped in June and started trending upward in July. A gradual increase has since persisted.

“Far more slowly than we did. It’s not as steep of a spike,” Vail said. “But it’s a lot of cases.”

She said vaccines slowed the increase, and the cases look different. They are younger. Older people are vaccinated at far higher rates. About 75% of people 50 and older are vaccinated in Michigan. That drops to 56% of people 30-49 and 43% of those under 30.

About 20% of cases now in Ingham County are people 17 years old or younger, Vail said last week.

What she sees now as a high-level plateau sets the state up for a potential surge in cases.

A spike should be expected in October or November, following what the state experienced last year, she said.

As more people gain immunity, either through infection or vaccination, the virus will settle into a more predictable, typical pattern, she said.

For now, the coronavirus is difficult to forecast.

“As you can see, the virus is anything but seasonal and every time people say this virus is a seasonal virus, that proves us wrong, because it is not a seasonal virus,” Sullivan said.

Read more on MLive:

Michigan reports 6,093 new coronavirus cases, 29 deaths in 3 days since Saturday, Sept. 11

See what Michigan public school districts have mask mandates

What we know about the Mu variant, and why delta remains biggest COVID-19 threat

Threat of fourth COVID surge in Michigan hospitals is ‘very real’ without more vaccinations

Weighing the risks of COVID vaccines against the risk of the COVID virus

Michigan researchers estimate combined vaccination, natural immunity rate

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