What to Know About Bivalent Booster Shots

The Centers for Disease Control and Prevention greenlit a new tool last fall for battling the pandemic: updated booster shots.

The bivalent booster shots were designed to target the Omicron subvariants BA.4 and BA.5, which were previously the dominant version of the virus. Since then, a new variant, XBB.1.5, has become dominant. But there may still be a benefit to getting the bivalent booster. Here’s what you need to know.

Where can I get the bivalent booster shot?

The bivalent vaccine is available at pharmacies and community health centers. Many mass-vaccination clinics across the country have closed, so you may have to seek out a new vaccination site. You can search a directory of sites at vaccines.gov.

Who is eligible?

The C.D.C. has recommended the Pfizer-BioNTech bivalent booster for anyone 6 months old or older if it has been at least two months since their last vaccination or booster shot. Children between the ages of six months and five years old who previously received a primary series of Moderna vaccines can get a Moderna bivalent booster if it has been at least two months since they completed their primary series. (The C.D.C. states that children between the ages of 6 months and 4 years should get the same product for their initial vaccines and their booster shots, if they are eligible.) People 6 years old or older can get the Moderna bivalent booster or the Pfizer booster if it has been at least two months since their last vaccination or booster.

For people who are under 65 and don’t have compromised immunity, there are no current recommendations for further vaccination after one bivalent shot. But the F.D.A. authorized an additional round of bivalent booster shots for adults 65 and older who have not received a bivalent booster in the last four months. The agency also approved another round of bivalent boosters for people with compromised immune systems who are at least two months out from their last bivalent shot.

If you have questions or concerns about your eligibility or your child’s eligibility, consult your primary care doctor.

How long should I wait to get the bivalent booster if I recently had a shot or got Covid?

Some experts recommend waiting longer than the F.D.A.-authorized period between shots. An advisory panel to the C.D.C. voted to recommend that same two-month interval between doses, although several members voiced concerns that it was too short.

Doctors and immunologists said that, in general, people should wait around four to six months after immunization or infection.

That’s because your body will probably not generate much of an immune response so soon after a previous encounter with the virus, said Aubree Gordon, an epidemiologist at the University of Michigan. “Your immunity level is so high that you’ll just neutralize immediately the antigen that’s being produced — you kind of reach a ceiling,” she said. “You don’t have that much higher to go.”

Once you do get the booster, it typically takes around one to two weeks after you get the shot for your antibodies to “kick in,” Dr. Gordon said.

Can you get the bivalent booster if you’re pregnant?

Yes. Booster shots are safe for pregnant people, Dr. Chin-Hong said, and just as with the initial vaccines, scientists expect that the antibodies a pregnant person generates could transfer to the baby once it’s born.

Does the bivalent booster offer better protection than past ones?

The previous booster shots provided robust protection against severe disease. There were, however, people who had breakthrough infections even shortly after receiving booster shots, including President Biden.

Emerging data indicates that the bivalent boosters may not provide strong protection against breakthrough infections, especially as the new subvariant XBB.1.5 edged out BA.4 and BA.5 and is now dominant. But the boosters continue to help protect against severe disease, said Dr. Justin Fiala, a pulmonary and critical care specialist at Northwestern Medicine.

“It still provides more protection than the original vaccine,” Dr. Chin-Hong said. “People still continue to say, ‘It doesn’t work.’ But that’s missing the point of serious disease, hospitalization and death.”

Will there be more boosters in the future?

It’s unclear whether this will be the last Covid booster offered, or whether there will be new boosters on a regular basis. The United States could offer the vaccine each year around the fall, similar to the flu vaccine, if the virus surges become predictable, Dr. Chin-Hong said.

But the pandemic’s trajectory has been anything but straightforward, and it’s hard to anticipate the state of the virus over the next few months, let alone the next few years. If the virus had not evolved, we probably would not need any new shots now, said Shane Crotty, a virologist at the La Jolla Institute for Immunology, adding, “It’s really up to the virus.”