COVID boosters are now approved by the CDC. Experts answer questions about the new vaccine.

On Tuesday, the Centers for Disease Control and Prevention (CDC) recommended that everyone 6 months and older get an updated COVID-19 vaccine to protect against the variants currently circulating in the U.S. The new shots from Pfizer-BioNTech and Moderna will be available later this week, per the CDC.

This follows the Food and Drug Administration's approval of the updated vaccines on Sept. 11, in an effort to make them available before respiratory illness season — including the flu and RSV — strikes in the fall.

The previous bivalent Moderna and Pfizer-BioNTech COVID-19 vaccines — which targeted Omicron subvariants BA.5 and BA.4 and the original SARS-CoV-2 virus — are no longer authorized for use in the U.S., per the FDA.

Here's what you need to know about the latest COVID boosters, according to infectious disease experts.

Who needs a COVID booster?

To date, getting a COVID-19 booster has been something that’s recommended after a person completes the initial COVID-19 vaccine series. The initial vaccine was designed to target the original strain of the virus, also known as the monovalent vaccine, Dr. William Schaffner, an infectious disease specialist at the Vanderbilt University School of Medicine, tells Yahoo Life. That was followed by bivalent shots that targeted multiple variants.

The new booster is monovalent, specifically targeting Omicron variant XBB.1.5, which has circulated heavily for months. “They made a big change with this one,” Dr. John Sellick, an infectious disease expert at the State University of New York at Buffalo, tells Yahoo Life.

Schaffner says that people who haven’t been vaccinated against COVID-19 will likely still need “at least one dose, and then periodically get these boosters as they become newly available.” However, that recommendation will ultimately be dictated by the ACIP.

Which variants does the booster target?

The updated booster is designed to target the XBB 1.5 strain of COVID-19. However, the current dominant strains in the U.S. are EG.5 (Eris) and FL.1.5.1, according to CDC data. The BA.2.86 variant, known as Pirola, has also been spreading, with the CDC warning that it “may be more capable of causing infection in people who have previously had COVID-19 or who have received COVID-19 vaccines.”

However, Schaffner says that “all the recent data would indicate that the updated booster will cover all of these variants.”

The booster focuses on the Omicron lineage, Sellick says. "This is Omicron genetic material, and the presumption is that this is going to provide protection against whichever of these Omicron descendants are circulating."

The FDA stated recent studies show the updated vaccines do help protect against the current variants going around right now, including EG.5 and BA.2.86. "This suggests that the vaccines are a good match for protecting against the currently circulating COVID-19 variants," according to the FDA.

Moderna, one of the pharmaceutical companies that manufactures COVID vaccines, said in a press release on Sept. 6 that the updated booster generated a nearly nine-fold increase in antibodies against Pirola (BA.2.86).

When will the booster will be available?

The booster will be available later this week, per the CDC. “The companies that make these vaccines probably have them packed up and ready to go,” Sellick says. Now that the CDC director has signed off on the updated vaccines, "the trucks will be pulling out like deployment of the Army,” he adds.

Who is recommended to receive the booster?

The CDC recommends that everyone 6 months and older get an updated COVID-19 booster "to protect against the potentially serious outcomes of COVID-19 illness this fall and winter."

How often will you need to get a booster?

That's still to be determined, but Sellick predicts that it will be recommended as an annual shot. “A lot of people have not been wild about getting any boosters,” he says. “Recommending something more often than annual is probably not going to work.”

Schaffner acknowledges that the currently available booster, which has been available for months, “has been underutilized by the population.” He adds, “We know that there’s vaccine fatigue out there.”

Will boosters keep being updated over time?

It seems that the booster will be updated on an annual basis. “The intention is to have everybody get a booster every year,” Schaffner says. “That program has not been finalized, but we’ve started the early steps moving in that direction.” Still, he adds, it’s important for people to be flexible just in case. “In the event the virus changes and mutates in some way, we may have to change our plan.”

Sellick says he anticipates that the COVID booster will be like the flu vaccine, that is, recommended every fall to help target whatever dominant strains are circulating at the time.

If you’re in a recommended demographic or category for getting the booster, Schaffner says it’s important to not hesitate. “Don’t underestimate this virus,” he says. “We anticipate that there will be an increase in cases this winter, and these variants are very contagious.”

This article was originally published on Sept. 11, 2023 and has been updated.