Who should get the Omicron booster? Here's what experts say.

COVID-19 booster shots that target the highly contagious Omicron variant — which managed to infect 90 million people worldwide in just 10 weeks — are around the corner.

The boosters were authorized by the Food and Drug Administration (FDA) on Wednesday, with shots expected to become available shortly after the holiday.

Both Pfizer-BioNTech and Moderna's new boosters target Omicron subvariants BA.5 and BA.4. Currently, BA.5 is the most common variant circulating in the U.S., responsible for nearly 90% of cases, according to the Centers for Disease Control and Prevention (CDC).

Here's what you need to know about the Omicron booster and who should get it, according to experts.

How is the Omicron booster different from the previous booster?

In a nutshell, the reformulated booster will provide a broader range of immunity, including better protection against Omicron variants.

When the original SARS-CoV-2 virus, which causes COVID-19, was identified, "there was one specific spike protein, which the vaccine was developed against," Dr. Mahdee Sobhanie, an infectious disease physician at the Ohio State University Wexner Medical Center, tells Yahoo Life. "Since the inception of the COVID vaccine, we have gone through multiple variants of concern, with the most recent one being Omicron."

Omicron has 37 mutations in the spike protein, making it better at evading protective antibodies from current vaccines or previous infections than the original coronavirus strain. While the current vaccines are holding up well against hospitalization, severe disease and death, "they do not elicit a high antibody response against Omicron subvariants, the most prevalent circulating variant globally, leading to potential immune escape," Dr. Jill Weatherhead, assistant professor of infectious disease at Baylor College of Medicine, tells Yahoo Life.

Both Pfizer and Moderna’s Omicron boosters are "bivalent" vaccines, meaning they protect against Omicron BA.5 and BA.4 subvariants and the original SARS-CoV-2 virus. "The goal of a COVID vaccine designed against the Omicron variant is to provide better protection against infection from the current circulating variant," says Sobhanie.

Do we actually need an Omicron booster?

Yes, say experts, since Omicron-targeting boosters offer greater protection against the highly contagious virus.

In general, the goal of new boosters is both to elicit a stronger immune response to current variants and to neutralize future variants, according to the FDA. "The thinking now is: How can we develop a vaccine that targets the circulating variant which is able to prevent infections rather than prevent severe disease?" says Sobhanie. "It is going to be interesting to see the data on how well the Omicron-specific boosters will be in preventing disease, and how long this protection will last."

Who is eligible to get the new booster?

Pfizer sought FDA approval of its Omicron booster for people 12 and older, while Moderna's is for those 18 and older. "Thus, it is possible that anyone who fits these age restrictions will be eligible for the updated vaccine,” says Weatherhead.

Younger pediatric groups are expected to follow. According to the CDC's fall vaccine planning guide, "at least one bivalent vaccine for children ages 11 years and younger may be authorized within a short time" after bivalent vaccines are approved for those 12 and older.

The CDC also states that the Omicron boosters will be available to those who have, at a minimum, already completed a primary series of COVID-19 vaccines.

Even if you had a second booster, though, experts say you can still get the Omicron booster. However, it's not yet known how soon after having an original booster shot that people will be eligible for the Omicron-targeting one.

When is the best time to get the Omicron booster?

Research shows that while protection against hospitalization remains strong with booster shots, protection from infection wanes over time, which is typical of vaccines in general. So there is some question about whether it's better to get the Omicron booster as soon as it's available or delay it a bit — say, until October — to have better protection through winter, when yet another COVID surge is expected. But experts recommend talking with your health care provider first, since they will factor in both your personal health risks and infection and hospitalization rates in your community.

"Right now there are areas where there are peaks and valleys of COVID circulation," notes Sobhanie. "People need to talk to their primary care doctors to see when it is best for them to get a booster, depending on how susceptible they are to developing severe disease."

Will there be more boosters in the future?

Don't be surprised if there are more reformulated boosters down the road. As the virus continues to spread and mutate, new boosters may be necessary to combat new variants, similar to how flu shots are reformulated each year depending on which flu viruses are making people sick in the lead-up to flu season.

"As the virus mutates and develops new variants, previous variations of the mRNA vaccine targeting ancestral SARS-CoV-2 strains will not be as effective," explains Weatherhead. That's why she says it's "important" that scientists are able to rapidly adapt COVID vaccines that "target the most prevalent circulating SARS-CoV-2 virus to provide the greatest protection possible."

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