NEW YORK (CBSNewYork) — While millions have yet to get their first COVID-19 shot, many are scrambling to get a third, their booster jab.

But which one and why? Those are the questions many people are asking about booster shots. Dr. Max Gomez clears up the confusion.

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It’s an odd situation — states and cities around the country not waiting for federal health authorities to authorize booster shots for their residents. In New York and Connecticut, anyone age 18 and older can get the third jab. New Jersey is expected to soon follow suit soon.

Dr. Jennifer Lighter, a hospital epidemiologist for NYU Langone Health, said the reason is simple.

“Booster shots increase your antibody levels and give the extra boost of protection,” Lighter said.

COVID VACCINE

Now comes the confusion. With three authorized vaccines for initial shots and for boosters, which booster should you get? Does it depend on which brand you got first? Which one will give you more protection?

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There are anecdotes floating around that the Moderna booster will cause more side effects because the dose is stronger, but that’s not true. The authorized Moderna booster dose is half the original strength. But if your doctor gave you an original strength Moderna dose as your third shot, rather than the approved booster dose, then you may have a stronger reaction to that jab.

So if you had Pfizer-Pfizer, can you get a Moderna booster? Or if you initially received Moderna-Moderna, or Johnson & Johnson, can you get Pfizer or Moderna as your booster? Again, Lighter says the answer is straightforward.

“Any of them are good and will create an increase in your antibody level,” she said.

CORONAVIRUS PANDEMIC

Better yet, those antibody levels rise faster than after the initial shots, so you could be protected by Thanksgiving. Having higher antibody levels has been shown to even provide decent protection against the Delta variant, which is especially important for pregnant women because COVID infection puts them at risk for pre-term delivery. And the vaccine even protects the baby.

“Antibodies travel from the placenta to the babies and the babies are protected as well for the first few months of life. So, pregnant women should definitely get boosted as well,” Lighter said.

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As for safety and side effects, several studies have shown the boosters to be safe, with no increase in significant adverse side effects. You’ll just experience the usual achiness, low-grade fever, headache, and fatigue that clears up in a day or so.

Dr. Max Gomez