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Your Guide To Adult Vaccines

Omicron Boosters: 9 Questions Answered About the Updated COVID-19 Shots

New bivalent vaccines target both the original coronavirus strain and some of 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

En español | Nearly two years 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 a few of the latest omicron subvariants, got the all clear from health officials in early September and are now available throughout the U.S.

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

1. 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 vaccines’ defenses.


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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.

Infection and transmission rates could go down with the introduction of the revised boosters, experts predict. So could hospitalization rates, which increased among older adults during the spring and summer. Modeling data shows that broad uptake of the new booster shots this fall could prevent more than 100,000 hospitalizations. Some projections say that number could be even higher — upwards of 745,000 hospitalizations averted.

“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 Medical Center.

And these updated boosters are key to that, adds Namandjé N. Bumpus, chief scientist at the U.S. Food and Drug Administration (FDA). They are “a really important tool to ensuring that we continue this trajectory toward a life that resembles normal,” Bumpus told AARP.

2. How are the new boosters different?

The updated boosters are 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 were widely circulating during the summer and early fall.

This, however, does not mean the updated boosters are a double-dose shot. They contain the same amount of 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.

3. Will they hold up against new subvariants that are circulating?

When the bivalent boosters were being made, omicron’s BA.4 and BA.5 were the greatest threats. BA.5 continues to circulate in the U.S. — it's responsible for about 24 percent of new COVID-19 cases, according to the CDC. But BA.4 is losing its steam, and other subvariants, like BQ.1, BQ.1.1 (both descendants of BA.5) and BF.7, are quickly gaining ground.

A big question on the minds of many: Will these new boosters still be able to stand up to other omicron subvariants? The short answer is yes, they should be able to, says the FDA’s Bumpus.

“The subvariants all have differences, but some similarities. And so by using these updated boosters that are developed to target omicron, specifically, we expect that there will still be a high level of protection against emerging subvariants.”

White House COVID-19 Response Coordinator Ashish Jha, M.D, had a similar response: “Based on everything we know right now, we believe that the brand-new updated COVID vaccines should provide a high degree of protection against BQ.1.1 and other subvariants that emerge,” he told AARP.

It’s really important to think about the fact that these updated vaccines, because they have a specific targeting, will help to update our immune system and give us the increase in protection that we need, especially as we look toward winter when more people are indoors. So I urge everyone to get the updated boosters and to really understand the fact that remaining up to date on our vaccines is a key part of keeping us as healthy as we can be.

— Namandjé N. Bumpus, chief scientist at the U.S. Food and Drug Administration

4. 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 6 and older and it’s been at least two months since your last shot. Pfizer’s vaccine is cleared for fully vaccinated people 5 and older along the same timeline.

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.

The goal, health officials have said, is to offer the booster on an annual basis, like the flu shot. That said, if the virus “starts genetically flip-flopping and doing more, well, we might have to [get boosted] a little more frequently,” Schaffner says. “But it remains to be seen.”

So far more than 35 million Americans have received the new bivalent shot; about 30 percent of Americans 65 and older have rolled up their sleeves.

Kenneth Koncilja, M.D., a geriatrician at Cleveland Clinic, is recommending that all his patients get the new booster. The reason? He saw more cases of COVID-19 in his hospital this summer than in past years. “And I’m worried about the fall and winter,” he said, pointing to the time of year when respiratory illnesses pick up.

Influenza activity is already increasing in most regions of the country, the latest CDC surveillance data shows. Cases of respiratory syncytial virus (RSV), which sends more than 177,000 older adults to the hospital each year, are also spiking.

“It’s really important to think about the fact that these updated vaccines, because they have a specific targeting, will help to update our immune system and give us the increase in protection that we need, especially as we look toward winter when more people are indoors,” Bumpus says. “So I urge everyone to get the updated boosters and to really understand the fact that remaining up to date on our vaccines is a key part of keeping us as healthy as we can be.”

5. If I just had COVID, should I wait on the booster?

If you just had COVID-19 — and millions did this summer and fall — 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.

6. What about safety and effectiveness?

A large CDC study published Nov. 22 found the new boosters provided "significant additional protection” against symptomatic COVID-19 in people who were at least fully vaccinated with the original (monovalent) vaccine. Vaccine makers Pfizer and Moderna have reached similar conclusions in clinical trials examining the effectiveness of the updated boosters, and no red flags have been raised when it comes to safety.

Pointing to the latest booster data, top infectious disease expert Anthony Fauci said in a Nov. 22 press conference, “We know it's safe. We know that it is effective. So, my message … is: Please, for your own safety, for that of your family, get your updated COVID-19 shot as soon as you're eligible to protect yourself, your family and your community.”

7. What are the side effects of the booster shots?

If you’re curious about what to expect when it comes to side effects from bivalent boosters, nothing is really different. The most commonly reported side effects among study participants who received a bivalent omicron (BA.1) booster shot from Moderna were in line with the side effects some people experienced after the initial vaccine and booster: pain, redness and swelling at the injection site; fatigue; headache; muscle pain; joint pain; chills; nausea/vomiting and fever. What’s more, Moderna reported that side effects from the BA.4/BA.5 bivalent booster were generally lower than previous vaccine doses. 

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. When it comes to the BA.4/BA.5 bivalent formula, Pfizer says the safety profile is similar to the previous version of the vaccine.

Experts have said 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.

8. 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.

And just like with the previous COVID-19 boosters and vaccines, these shots are free.

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

Yes. And in fact, experts are encouraging it.

“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.

Can the vaccine help prevent long COVID?

Millions of Americans have experienced what’s called long COVID, or new or lingering symptoms of the illness that persist several weeks or months after the initial infection. And while anyone can get long COVID, researchers are working to understand if certain groups of people are at higher risk for it, and why. According to the Centers for Disease Control and Prevention, one population that’s more likely to suffer from long COVID is unvaccinated individuals.

“What the data is showing so far is that staying up to date on COVID-19 vaccines does appear to significantly reduce the risk of long COVID, especially compared to no vaccine,” says Namandjé N. Bumpus, chief scientist at the U.S. Food and Drug Administration (FDA). “So another reason why it’s really important to stay up to date on vaccines, and certainly what we can think of as another beneficial effect of vaccination, is that reduction in the risk of long COVID.”

Why Do I Need the New COVID Vaccine Booster?

Editor’s Note: This story, originally published Sept. 6, 2022, has been updated to reflect new information.

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.