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CNN  — 

US Centers for Disease Control and Prevention Director Dr. Rochelle Walensky endorsed recommendations for booster doses for Moderna’s and Johnson & Johnson’s coronavirus vaccines Thursday, allowing millions more Americans to begin getting booster shots.

Walensky also endorsed the mix-and-match approach to boosters, saying eligible people could choose whichever vaccine they wished as a booster.

The CDC re-aligned its recommendation for the existing recommendation for Pfizer boosters, placing Moderna’s and Pfizer’s boosters in the same category.

“For individuals who received a Pfizer-BioNTech or Moderna COVID-19 vaccine, the following groups are eligible for a booster shot at 6 months or more after their initial series,” it said.

They include people:

• 65 years and older

• Age 18+ who live in long-term care settings

• Age 18+ who have underlying medical conditions

• Age 18+ who work or live in high-risk settings

“For the nearly 15 million people who got the Johnson & Johnson COVID-19 vaccine, booster shots are also recommended for those who are 18 and older and who were vaccinated two or more months ago,” it added.

“These recommendations are another example of our fundamental commitment to protect as many people as possible from COVID-19. The evidence shows that all three COVID-19 vaccines authorized in the United States are safe – as demonstrated by the over 400 million vaccine doses already given. And, they are all highly effective in reducing the risk of severe disease, hospitalization, and death, even in the midst of the widely circulating Delta variant,” Walensky said in a statement.

The CDC’s Advisory Committee for Immunization Practices had just hours earlier voted to accept the US Food and Drug Administration emergency use authorizations for each vaccine – after considerable discussion about whether such broad authorization was needed for Moderna’s.

Members agreed that people who got Johnson & Johnson’s vaccine need a second vaccination, as that vaccine is less effective than Moderna’s and Pfizer’s in preventing infection.

“There are now booster recommendations for all three available COVID-19 vaccines in the United States,” the CDC said.

“Eligible individuals may choose which vaccine they receive as a booster dose,” it added.

“Some people may have a preference for the vaccine type that they originally received and others, may prefer to get a different booster. CDC’s recommendations now allow for this type of mix and match dosing for booster shots.”

Already, the pace of Americans getting booster doses is higher than the rate of those being vaccinated for the first time. CDC officials and others have made it clear the best way to reduce spread of the coronavirus is to get more people vaccinated in the first place.

“Millions of people are newly eligible to receive a booster shot and will benefit from additional protection. However, today’s action should not distract from the critical work of ensuring that unvaccinated people take the first step and get an initial COVID-19 vaccine. More than 65 million Americans remain unvaccinated, leaving themselves – and their children, families, loved ones, and communities– vulnerable,” the CDC said in Thursday’s statement.

“Available data right now show that all three of the COVID-19 vaccines approved or authorized in the United States continue to be highly effective in reducing risk of severe disease, hospitalization, and death, even against the widely circulating Delta variant. Vaccination remains the best way to protect yourself and reduce the spread of the virus and help prevent new variants from emerging.”

CDC officials said they’d issue more guidance on boosters in an upcoming report.

They said, for instance, that young women, who have a higher risk of rare blood clots from the J&J Janssen vaccine, might want to consider using one of the mRNA vaccines – Pfizer’s or Moderna’s – as a booster, while young men, who have a higher risk of an inflammatory heart condition known as myocarditis from an mRNA vaccine, might prefer Janssen’s vaccine for a booster if needed.

At least one ACIP member expressed concern about recommending boosters for such a broad population.

“I would try to mitigate the harm by having some age restriction on the otherwise worried well. Because we don’t usually have vaccines because we have the worried well,” said Dr. Sarah Long, a professor of pediatrics at Drexel University College of Medicine.

Long said she thought offering boosters to people who may not really need them would encourage them to get them, anyway, perhaps risking side-effects.

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“I echo Dr. Long’s feeling that there are probably many people who are going to get a Moderna booster who don’t need it,” said ACIP member Dr. James Loehr, owner of Cayuga Family Medicine in Ithaca, New York.

“However, given the situation that we’ve already approved the Pfizer, and there are enough people who are looking for a booster, I’m inclined, reluctantly, to just go ahead and recommend a similar pattern for the Moderna booster, with much stronger feelings in favor of the Janssen booster.”

“The Johnson & Johnson vaccine provided 94% protection in the U.S. against COVID-19 when given as a booster following the single-shot Johnson & Johnson vaccine, and due to its unique mechanism of action, offers long-lasting, durable protection,” Dr. Paul Stoffels, chief scientific officer at Johnson & JOhnson, said in a statement. “We remain confident in the benefit it will provide to millions around the world.”