Pfizer vs Moderna: what are the differences between the new bivalent boosters?

(NEXSTAR) — Americans looking to get a coronavirus shot this fall don’t have just one new option — they have two. Both Moderna and Pfizer have a new FDA-cleared COVID-19 vaccine specially formulated to ward off the omicron variant of the virus.

Both vaccines are bivalent, meaning they contain parts of the original COVID-19 strain and the omicron strain that became dominant in 2022.

The new shots from both companies are very similar. Here’s what you need to know if you’re trying to choose between the two.

Who is eligible for each type of booster?

That’s the main difference between Pfizer’s and Moderna’s bivalent booster: Moderna is cleared for adults 18 and older, while Pfizer is cleared for anyone 12 and older, according to the Food and Drug Administration.

Both boosters are recommended by the Centers for Disease Control and Prevention at least two months after your last dose.

Is there something different in the composition of the Pfizer and Moderna shots?

The two bivalent boosters are mRNA injections, created much like the original vaccines released nearly two years ago. They also both contain the original COVID-19 strain and the omicron strain, designed to give you maximum protection against the variants currently circulating.

Pfizer and partner BioNTech say their new booster contains 15 micrograms each of coding for the spike protein from the original COVID variant and BA.4/BA.5 subvariants of omicron. Moderna contains a little more: 25 micrograms of each type.

A single Moderna booster dose is 0.5 milliliters, while a single Pfizer booster dose is 0.3 milliliters.

Can you mix and match? Should you?

Adults are allowed to mix and match brands, which means even if you’ve always had Pfizer, you can upgrade to Moderna now (and vice versa). People between the ages of 12 and 17 should still stick to Pfizer for now.

But just because you can mix and match, is there an advantage? When we asked Dr. Bob Wachter, chair of the Department of Medicine at the University of California, San Francisco, about the prospects for mixing and matching last year, he said changing things probably wouldn’t significantly strengthen your immunity.

However, if you had a bad reaction to any of the brands with a previous dose, he said, you should talk to your doctor about switching vaccine types.

Do Pfizer and Moderna have different side effects?

It is too early to have solid studies on whether these two booster brands have different side effects from each other. However, evidence from both clinical trials shows that the side effects of the bivalent injections are similar to the side effects of the last booster shot and the original vaccine.

“Most commonly it’s redness at the inoculation site, pain, feeling tired for a day or two afterwards – all the same side effects we’re seeing at about the same rates with the booster bivalent,” Andrew Pekosz, a virologist at the Johns Hopkins Bloomberg School of Public Health, said at a recent press conference.

Other common side effects include headache, fever, chills and nausea, according to the CDC.


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