FDA signs off on Novavax COVID vaccine. Here's how it's different from other shots.

A third COVID-19 vaccine, made by Novavax, will soon be available in pharmacies and doctor's offices.

The Food and Drug Administration Tuesday authorized use of the Novavax vaccine, which is based on a different type of technology than the other two available vaccines.

Both types of shots train the immune system to identify and target the spike protein found on the surface of the SARS-CoV-2 virus. The Pfizer-BioNTech and Moderna vaccines use messenger RNA technology, while the Novavax vaccine uses a protein to do the same thing.

The FDA authorization enables the Novavax shot to be used as a booster in people ages 12 and up.

How are the shots different?

The mRNA technology had never been used in an approved vaccine before COVID-19, though it was under development for a number of years.

The body uses messenger RNA to turn a DNA blueprint into the proteins needed for cellular activity. In the case of COVID-19 vaccines, the mRNA delivers a blueprint to manufacture the spike protein.

A key advantage to mRNA vaccines is they can be developed very quickly – so far in about six weeks – which is why they are already available.

Protein-based vaccines, by contrast, have been around for a long time, used to prevent hepatitis B, pertussis, pneumonia and meningococcal disease, among other diseases.

But they typically take longer and are more complicated to manufacture. It takes about four months for Novavax, which makes its vaccines in insect cells, to transform from a genetic sequence of a viral variant to a vaccine.

The Novavax vaccine directly delivers large numbers of the spike protein to the body, rather than having the body manufacture it itself, as the mRNA shots do. The Novavax vaccine also includes an "adjuvant," an added ingredient that amplifies its effect.

Is it worth mixing and matching?

Getting either an mRNA or Novavax' protein-based vaccine probably doesn't make much of a difference to the immune system. Studies show that a healthy immune system produces about as many neutralizing antibodies after a boost with either type of vaccine, said John Moore, a virologist at Cornell University's Weill Cornell Medicine in New York.

But Moore, who was a volunteer in Novavax's Phase 3 research trial back in 2021, plans to get a Novavax booster in a few weeks before a scheduled trip abroad in early November.

People who had a sore arm or headaches after an mRNA shot may have less of a reaction after the Novavax vaccine, Moore said.

What variant is targeted?

The Novavax vaccine targets the same XBB.1.5 variant as the other two vaccines.

That variant was the dominant one in the U.S. earlier this year when the FDA had to choose the makeup of this fall's vaccine. Officials knew it would no longer be dominant by now, which it isn't.

But all indications so far are that the new vaccine is effective at protecting against severe disease caused by current circulating variants, which all remain descendents of omicron.

The EG.5 variant accounts for nearly 30% of infections in the United States, with FL.1.5.1 accounting for just under 14%, HV.1 just under 13%, and XBB.1.16.6 about 10%. About two-dozen more variants make up the balance.

Where will Novavax be available?

Like the mRNA vaccines, which have been available for the last several weeks, the Novavax shot will soon be widely accessible.

Once the FDA signs off on the batches, as is standard practice and expected to take no more than a few days, the Novavax vaccine will be available in Costco, CVS Pharmacy and Rite Aid, among other locations. It will also be available through the Vaccines for Children and Bridge Access Program, which provides free shots.

Contact Karen Weintraub at kweintraub@usatoday.com.

Health and patient safety coverage at USA TODAY is made possible in part by a grant from the Masimo Foundation for Ethics, Innovation and Competition in Healthcare. The Masimo Foundation does not provide editorial input.

This article originally appeared on USA TODAY: Novavax COVID vaccine gets FDA thumbs up: Comparing it to other shots