By Karli Barnett

MIAMI (CBSMiami) – The CDC just approved the COVID vaccine for younger children, but that may leave adults wondering what is next for them.

For many people who are fully vaccinated, it may be time for shot number three.

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President Joe Biden spoke at the White House Wednesday, encouraging those are eligible to get their booster.

“Older Americans, by far, are the most vulnerable at getting the sickest, and boosters add an important layer of protection,” he said. “They are free and effective.”

CBS4 spoke with Dr. Carla McWilliams, the Chief of Infectious Disease at the Cleveland Clinic Weston Hospital, to find out who really needs a booster and when.

“When we look at people who are immunocompromised, or much older, as we get further out from completing that vaccine series, we have seen an increase in the risk of vaccine waning immunity and more severe infections. That’s the primary basis of the booster,” she explains.

The CDC recommends the booster for people 65 and older, people 18 and older with underlying medical conditions, and people 18 and older in high-risk settings, such as first responders, healthcare workers, education staff, and grocery store workers.

“For those individuals who have received a J&J vaccine, you would be eligible for a booster two months after your initial dose,” says Dr. McWilliams.  “For the mRNA vaccines, you are eligible for a booster six months after completion of the primary series.”

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When it comes to the boosters, you can “mix and match,” so to speak.

“If somebody had an initial dose with the J&J and they wanted to have a booster with an mRNA vaccine, whether it’s Pfizer or Moderna, they could certainly do that, and vice versa. If you were initially immunized with the Moderna series and wanted to have a Pfizer boost, or if that’s the only available vaccine for a booster, you could do that,” she explains.

An antibody test is also not an effective way of determining who needs a booster.

“We still don’t have enough data to tell us what an adequate antibody titer is,” Dr. McWilliams says. “How do you interpret the test if you don’t know the number that’s going to confer the protection you’re looking for? So this is the justification for why we do not recommend any antibody screening to determine what your level of risk is, or how you’ve recovered from illness, or a vaccine response.”

South Florida may be experiencing a bit of a lull in positive cases, but Dr. McWilliams still encourages people, especially ahead of the holidays, to get their initial doses if they have not done so.

“As someone who works in a hospital treating COVID patients, I can tell you the majority of people we see are unvaccinated,” she says.

Common side effects of the booster are similar to those of the other doses, such as sore arm, fatigue, and headache.

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Boosters are currently available at Publix Pharmacies, CVS, Walgreens, and Broward and Miami-Dade vaccine sites.

Karli Barnett