(CNN) — The US Food and Drug Administration authorized Novavax’s Covid-19 vaccine on Friday for emergency use in adolescents. It is the fourth coronavirus vaccine available in the United States and, unlike the others, it uses a protein-based technology.

The vaccine was authorized for adults in July. With the latest emergency use authorization, it also will be available as a two-dose primary series for ages 12 to 17.

In this age group, “overall, the clinical efficacy of the vaccine is around 80%,” said Silvia Taylor, Novavax’s senior vice president global corporate affairs. The vaccine has shown 90% overall efficacy in adults.

Novavax announced in early July that its vaccine shows “broad” immune response to currently circulating variants, including the Omicron subvariants BA.4 and BA.5.

“One of the things that we believe makes our vaccine unique is that we actually see really good immune response against variants with our prototype vaccine. And so, if you think about the vaccine that we already have authorized that we’re talking about now to be authorized for adolescents, we actually see a good immune response against variants including Omicron, including BA.1 and BA.5,” Taylor said.

Protein-based vaccines use a more traditional approach than mRNA vaccines, teaching the immune system to recognize little modified pieces of the virus that the vaccine is targeting. In this case, that means fragments of the coronavirus spike protein. The vaccine was created out of a genetic sequence of the original strain of the coronavirus.

This technology is also used for vaccines for conditions such as hepatitis B and pertussis.

Taylor told CNN that having a protein-based coronavirus vaccine available helps give adolescents more options.

About 60% — or 15.2 million — of all 12- to 17-year-olds in the US are fully vaccinated against Covid-19, according to the US Centers for Disease Control and Prevention, as of Friday.

“We believe fundamentally that people want a choice in the vaccines that they’re able to have for themselves, and especially in this population that we’re talking about for children,” Taylor said. “So, we think that that kind of reassuring technology platform that’s understood, combined with the high levels of efficacy and the well-tolerated safety profile, can help increase that vaccination number in children.”

Next, Novavax plans to have trial data on using the vaccine among children younger than 12.

“We recently initiated a trial that we’re calling Hummingbird, which is a Phase 2b/3 trial, and that’s going to be an effectiveness and efficacy trial and also clearly be looking at safety, and that will have three age cohorts,” Taylor said, referring to groups of children ages 6 to 11, ages 2 to 5, and 6 months to 23 months.

“The first cohort of kids, that trial was already initiated, and that’s for kids 6 to 11,” Taylor said. “We expect those results in the early part of 2023.”

Novavax is working on an updated version of its vaccine that specifically targets the Omicron coronavirus variant and its subvariants — and the company could file for authorization later this year, she said.

“Our intent is to file for authorization of a BA.5-containing bivalent form of a vaccine in the fourth quarter of this year,” Taylor said.

“This is consistent with the approach that other manufacturers are following,” she said. “We would submit that for formal authorization for EUA, just like we did for other indications to the US FDA.”

FDA authorizes Novavax Covid-19 vaccine for emergency use in ages 12-17