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Omicron Boosters: What to Know About the Updated COVID-19 Shots

New bivalent vaccines target both the original coronavirus strain and the latest variants

Travelers walk past a sign offering free COVID-19 vaccinations and booster shots at a pop-up clinic in the airport

FREDERIC J. BROWN / Getty Images

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Roughly a year and a half after their debut, the COVID-19 vaccines have received an update.

The retooled shots from Moderna and Pfizer-BioNTech, which are formulated to better target the omicron variants that are currently circulating, have the all clear from health officials and are now available at many doctor offices, pharmacies and health clinics throughout the U.S.

Here’s what you need to know about the latest boosters, including when you can receive one.

Why do we need new boosters?

The COVID-19 vaccines first developed in 2020 have saved millions of lives worldwide — upwards of 20 million, some estimates show — and have helped keep countless individuals out of the hospital. But the virus that the original vaccines and boosters were designed to fight has changed in the last two and a half years, and the latest versions are better at evading the vaccine’s defenses. The goal of the updated boosters is to “help restore protection that has waned since previous vaccination” and “to provide broader protection against newer variants,” Centers for Disease Control and Prevention (CDC) Director Rochelle Walensky, M.D., explained.


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Infection and transmission rates could go down with the introduction of the revised boosters, experts predict. So could hospitalization rates, which the CDC says have increased among older adults since April 2022. Modeling data show that broad uptake of the new booster shots early this fall could prevent more than 100,000 hospitalizations.

“The major goal continues to be prevention of hospitalization and prevention of serious disease,” says William Schaffner, M.D., a vaccine expert and professor of medicine at Vanderbilt University School of Medicine.

How are the new boosters different?

The updated boosters are so-called bivalent vaccines, meaning they contain not one, but two sets of instructions (mRNA) that teach the body to produce antibodies to fight off a coronavirus infection.

One mRNA component is from the original strain of the coronavirus. This is “to provide an immune response that is broadly protective against COVID-19,” the FDA says. The other is from omicron’s BA.4 and BA.5 variants, which are the current threats in the U.S. and around the globe. According to the CDC, BA.5 is responsible for about 90 percent of new COVID-19 cases in the U.S.; BA.4 makes up the rest. And both are expected to continue circulating this fall and winter.

This, however, does not mean the updated boosters are a double-dose shot. They contain the same amount of so-called antigen as the original vaccines.

Now that the new boosters are available, the older versions will no longer be used. (Much like how you don’t get last year’s influenza vaccine for this year’s flu season.) However, the primary series of the COVID-19 Pfizer and Moderna vaccines will remain the same for now, meaning the first two shots given to people who have not been vaccinated will only contain mRNA components from the original strain of the coronavirus.

Who is eligible for the new boosters?

It doesn’t matter how many boosters you have under your belt right now — none, one or two. As long as you’ve had your primary series, you can get an updated Moderna booster if you are 18 and older and it’s been at least two months since your last shot. Pfizer’s vaccine is cleared for fully vaccinated people 12 and older along the same time line.

This doesn’t necessarily mean you’ll need to get boosted every two months from here on out, though. “What the interval will be is currently not known,” Schaffner says, adding that a lot will depend on how often the virus mutates and to what extent.

“If the virus is reasonably stable, maybe we only have to do this on an annual basis. If it starts genetically flip-flopping and doing more, well, we might have to [get boosted] a little more frequently. But it remains to be seen,” he says.

Vaccine uptake will likely be high among older adults, who are at high risk for some of the worst complications of COVID-19. A recent University of Michigan poll shows that 61 percent of people over the age of 50 who have already had at least one dose of the COVID-19 vaccine are very likely to go back for an updated booster shot.

Kenneth Koncilja, M.D., a geriatrician at Cleveland Clinic, is recommending that all his patients get the new booster as soon as it’s available. The reason? He saw more cases of COVID-19 in his hospital this summer compared to past years. “And I’m worried about the fall and winter,” he said, pointing to the time of year when respiratory illnesses pick up. “This really could be a game changer for our public health.”

If you just had COVID-19 — and millions did this summer — talk to your doctor about the best time to get your next booster. Reinfection is less likely in the weeks to months after infection, the CDC says, so if you don’t have any underlying risks and infection rates aren’t particularly high in your area, it may be appropriate to hold off a little longer (about three months) for your booster.

What about safety and effectiveness?

The data reviewed by the FDA and CDC included clinical trial results looking at a slightly different COVID-19 bivalent booster: one that included the original coronavirus strain and BA.1, which like BA.4 and BA.5, is a subvariant of omicron. Mouse studies looking at the safety and effectiveness of the BA.4/5 bivalent vaccine were also considered; clinical trial results in humans are forthcoming.

When it comes to effectiveness, the bivalent BA.1 boosters generated a stronger immune response than the first-generation vaccines, top infectious disease expert Anthony Fauci, M.D., explained in a Sept. 6 press briefing. “And so we fully expect that the updated bivalent vaccines containing BA.4/BA.5 sequences will offer better protection against currently circulating strains than the original vaccines,” Fauci added.

What’s more, no safety concerns were raised from the bivalent studies. Peter Marks, M.D., director of the FDA’s Center for Biologics Evaluation and Research, said that the FDA has been planning for the possibility of updated COVID-19 vaccines and worked with experts and manufacturers to make sure the process was safe.

“The FDA has extensive experience with strain changes for annual influenza vaccines. We are confident in the evidence supporting these authorizations,” Marks said.

If you’re curious about what to expect when it comes to side effects from bivalent boosters, nothing is really different. Among the study participants who received Moderna’s bivalent BA.1 vaccine, the most commonly reported side effects were in line with the side effects some people experienced after the previous boosters: pain, redness and swelling at the injection site; fatigue; headache; muscle pain; joint pain; chills; nausea/vomiting and fever.

Pfizer’s bivalent BA.1 study yielded similar results, with the most commonly reported side effects being pain, redness and swelling at the injection site; fatigue; headache; muscle pain; chills; joint pain; diarrhea and fever.

No adverse events were reported in either study, though experts say they will continue to keep an eye on the rare risk of myocarditis, an inflammation of the heart muscle that can weaken the heart in younger adults.

Where can I get an updated booster?

The updated boosters are available at many of the same sites that have been administering COVID-19 vaccines and boosters all along — pharmacies, doctor offices, community health centers, etc. You can find the closest location on vaccines.gov.

Vaccine manufacturers began shipping the updated shots soon after they received the green light from health officials, so the shots should be trickling in. That said, it never hurts to call ahead of time to make sure they’re in stock at your preferred location. And just like with the previous COVID-19 boosters and vaccines, these shots are free.

Can I get it at the same time as a flu shot?

Yes. And in fact, the timing is perfect, since the ideal window to get the flu shot is in September or October, the CDC says.

“I like to say in a kind of a casual way this year, it means you’ll have to roll up both sleeves,” Schaffner adds.

Like with COVID-19, older adults are at greater risk for complications from the flu, so an influenza vaccine is a great way to reduce the likelihood that you’ll end up in the hospital. What’s more, this year’s flu season is expected to hit harder than the last few, “so getting the flu vaccine will be important,” says Priya Sampathkumar, M.D., a critical care and infectious disease specialist at Mayo Clinic.

Be sure to ask for a high-dose flu shot if you are 65 or older. And while you’re at your doctor’s office or pharmacy, check with your provider to see if you’re up to date on other important immunizations, like the shingles and polio vaccines, Sampathkumar adds. Adults 65 and older should also receive a pneumococcal vaccine.

Why Do I Need the New COVID Vaccine Booster?

Rachel Nania writes about health care and health policy for AARP. Previously she was a reporter and editor for WTOP Radio in Washington, D.C. A recipient of a Gracie Award and a regional Edward R. Murrow Award, she also participated in a dementia fellowship with the National Press Foundation.