People 50 and older may now get a second COVID-19 booster shot.

The U.S. Food and Drug Administration and the U.S. Centers for Disease Control and Prevention this week updated its booster recommendations, expanding eligibility requirements for what is for most a fourth dose.

This news comes as COVID-19 transmission is down in Michigan. Hospitals are largely focused on other patients and most people, if they hadn’t already months ago, have resumed unrestricted outings and activities.

Here, experts address questions for those considering a third or fourth vaccine dose.

So, what happened?

The FDA authorized a second booster dose of either the Pfizer or Moderna COVID-19 vaccines for people 50 and older and those 12 and older with certain kinds of immunocompromise, including those who have received solid organ transplants or are living with conditions that bring about an equivalent level of immunocompromise. (Pfizer’s vaccine is the only one authorized for children so those 12 to 17 are only eligible for Pfizer booster shots.)

The shots are to be administered at least four months after receipt of the first booster dose of any authorized or approved COVID-19 vaccine.

Previously, the FDA authorized a single booster dose for people with compromised immune systems after they have completed a three-dose primary vaccination series.

RELATED: Michigan study shows booster shots reduce mortality even among older, sicker COVID patients

Why were the recommendations updated?

The federal agencies acknowledge the increased risk of severe disease in certain populations, those who are elderly or older and with multiple underlying conditions.

These conditions include: Cancer; chronic kidney, liver or lung disease; cystic fibrosis; dementia or other neurological conditions; diabetes; heart failure or coronary artery disease; disabilities like cerebral palsy or down syndrome; or HIV infection.

Vaccine protection appears to wane at about six months, and many at-risk Americans received booster shots that long ago, said Dr. Russell Lampen, adult infectious disease physician and medical director of infection prevention at Grand Rapids-based Spectrum Health.

Booster shots were first recommended for the most vulnerable groups in September.

“So, this provides them an opportunity to get boosted and to improve their immunity and increase their levels of protection against future COVID surges or infections,” Lampen said.

RELATED: Hospitals report 85 to 95% of patients with COVID-19 have not had booster shots

What do they know about second booster shots?

Data is limited and mostly based on information from Israel, where authorities approved a fourth COVID-19 dose for people 60 and older.

“I don’t think the science is rock solid on who absolutely needs it,” said Dr. John Brooks, medical director of infection prevention for McLaren Health Care, based in Grand Blanc, and chair of the emerging pathogens task force.

He sees federal authorities trying to be consistent, first boosting older and sicker people. Determining what groups should receive another round of extra shots “probably needs to be teased out a little bit,” said Brooks, confident that “we’ll get there.”

In a study of people 60 and older in Israel, those who received the second booster were 78% less likely to die, according to a March 24 preprint. The analysis looked at about 563,000 people. Of those, 328,597 received the second booster and 92 of them died. Among those who only had one booster, 232 died, found researchers from a university and Clalit Health Services, an Israeli insurer.

A preliminary data analysis from the Israel Ministry of Health found the fourth dose raised protection against infection by up to two times compared to those who had three doses. It raised protection against severe illness by up to three times and higher. The study looked at about 1 million adults 60 and older. About 400,000 of them had received the second booster.

Another study from Sheba Medical Center in Israel and the Ministry of Health, which looked at 1,050 health care workers, found a fourth dose of mRNA vaccine is immunogenic, safe and “somewhat efficacious,” primarily against symptomatic disease. About 18 to 21% of those who had received the second booster were infected with the omicron variant compared to about 25% in the control group and most participants reported negligible symptoms.

Results suggest “maximal immunogenicity” is achieved after three doses and antibody levels can be restored by a fourth dose. In healthy young health care workers, the benefits may only be “marginal.”

So if I am in my 50s and relatively healthy do I need the second booster?

“I wouldn’t be running to the pharmacy to get that dose at this stage of the game,” Brooks said of healthy people in their 50s.

Most of the data does not look at the benefits for younger people.

Past studies have shown for people who are 45, healthy and up to date on their vaccinations, meaning they have had three doses of mRNA vaccines, the risk of death is very low, Lampen said, noting it is more likely this population will die while driving than of COVID-19.

So who most benefits?

Getting another booster shot makes more sense for those who are older and sicker, doctors said.

“If you are 80 and you have hypertension, I’d be running to the pharmacy for the fourth dose. Because we know it makes a difference,” Brooks said.

In octogenarians and older people, their immune response is “relatively poor.” “And so, if they’re willing to keep that ramped up, it will keep them healthy from COVID,” Brooks said.

Lampen said people who are 50 and older who have medical comorbidities also should consider it.

Vaccinations are not “quite as bulletproof” for individuals of advanced ages and with existing conditions, he said.

But transmission is low right now in Michigan. Should I do it now?

Percentages of positive tests and numbers of new cases are lower than they have been since summer. “It is difficult to motivate people to get vaccinated when people aren’t sick,” Lampen said.

However, the best time to get vaccinated is two weeks before the next variant or surge. “Which we really don’t have any idea when that will be,” Lampen said.

Someone who is at high risk should think about it now, rather than wait, he said.

Brooks noted the BA.2 omicron subvariant is circulating. Europe, which quickly relaxed pandemic restrictions, has seen increases in Britain, Italy, Germany and elsewhere. Parts of Asia, where communities were under among the most stringent safety measures, also are seeing swells.

BA.2 now is the dominant strain in the United States and it said to make up about 50% of cases in the region containing Michigan, according to the U.S. Centers for Disease Control and Prevention, but cases are not dramatically increasing. Hospitalizations are on a decline.

The hope is that Michigan has sufficient natural and vaccine-induced immunity after the huge surge of cases during the winter to protect the state from the BA.2 wave.

Should I time a booster dose with a big upcoming event or trip?

This reminds Lampen of a question posed to financial advisors about when to put money into the stock market and when to remove it.

It is impossible to know for sure. “You can’t game the market. You have to just put the money in and leave it in,” Lampen said.

He would be reluctant to advise waiting until an optimal life moment.

Are there any drawbacks or side effects?

Lampen said the incoming data shows an improvement in antibody production without any significant, serious consequences.

He said with mRNA vaccines, doctors or experts have not seen any blunted immune response.

Brooks said the vaccines are “extraordinarily safe.” The only difficulty is the time and energy it takes to attain the dose, he said.

A lot of people haven’t gotten the first booster. Should we be talking about a second?

In Michigan, about 59.5% of people who are 12 and older and fully vaccinated have received a booster shot. (Some fully vaccinated residents might not be eligible, depending on when they completed their primary series, but the numbers of new vaccinations have gone almost stagnant in recent months.) Younger people are much less likely to have been boosted than older people.

Lampen would like to present a dual message here. People who have not gotten a booster dose, recommended for everyone 12 and older at least five months after completing an mRNA series, should do so. (Those who received the Johnson & Johnson primary vaccine should receive an mRNA booster at least two months later, the CDC says.)

Brooks recognizes that in some parts of the world, people do not have access to any vaccines at all, and as long as there are unprotected parts of the world, the virus can infect and mutate.

Are we going to have to keep getting shots every several months?

The hope is COVID-19 will become more like influenza, doctors said. There would be a yearly event, and authorities would administer an annual, tailored vaccine to coincide with seasonal illness. The United States is not yet at this point. “It still is spreading widely. It is not meeting any sort of seasonal pattern,” Lampen said.

What if I just had COVID-19?

People should be out of the infectious period and isolation, Brooks said. They need to wait at least 10 days.

Brooks said he often advises his patients to give it 30 or more days. This way, they tend to experience fewer side effects, and natural infection protects patients for 30 to 90 days. “So, I don’t see a lot of risk.”

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