The COVID-19 booster shots are getting an upgrade. Federal health authorities greenlit the long-awaited reformulated boosters by Moderna and Pfizer for people ages 12 and older last week.
The booster vaccines are modified to better protect vaccinated people against hospitalization and death from newer viral variants. They are bivalent, meaning they can target the original COVID-19 strain as well as Omicron BA.5, the dominant variant in the United States.
Health officials emphasized the timeliness of the updated booster rollout, as people will spend more time gathered indoors in the fall and winter. Making the new booster shots available in September would avert thousands of deaths and hospitalizations compared to a November campaign, researchers told a CDC advisory panel last week.
Just how effective are the new boosters and when should you get yours? Here’s what we know so far.
Teens and adults eligible for the booster can only get the reformulated shot moving forward. If you received a Novavax or Johnson & Johnson primary series, you can still get a booster shot by Pfizer or Moderna.
Here’s the breakdown by age groups:
If you're immunocompromised, you might have received more than one booster shot already, and you can get the new booster two months after your last vaccine.
The bivalent boosters are not entirely new vaccines. Moderna and Pfizer modified their existing vaccines to target different versions of the COVID-19 virus. The new booster is designed to protect against the original strain and Omicron subvariants BA.4 and BA.5.
Both Pfizer and Moderna’s bivalent boosters are the same dose size as the previous version. Pfizer's vaccine contains 30 micrograms of antigen, while Moderna's contains 50 mcg. In each vaccine, half of the dose protects against the newer Omicron variants, while the other half is the original vaccine formula.
Earlier this year, Moderna and Pfizer conducted clinical data on bivalent vaccines geared toward Omicron BA.1, which drove a peak in cases at the beginning of 2022. In both trials, the boosters spurred high levels of protective antibodies in the study participants.
Both companies also shared data on how bivalent vaccines that target BA.4 and BA.5—the more current strains—performed in mice. The Moderna bivalent vaccine boosted neutralizing antibodies in mice more than 4-fold, while mice inoculated with the Pfizer bivalent booster saw a 2.6-fold increase in antibodies.
There's no data yet on just how well the now-approved boosters actually work in humans. Moderna has enrolled participants in its clinical study to test the BA.4/BA.5 vaccine and it said it expects data by the end of the year. Pfizer is also testing its own booster in clinical trials, as well as its BA.1 bivalent booster in children 6 months to 5 years old.
After recovering from COVID-19, your body has a high level of immune cells geared up to protect against reinfection. Memory B cells ensure that the body remembers how to make neutralizing antibodies for some months after.
The CDC said people with a prior infection can technically get a booster as soon as they've recovered. However, a recent preprint study indicates that the immune system doesn't gain much by getting a booster within two months after recovery.
“For persons who have had prior COVID-19, the recommendation is to generally wait at least three months before giving the dose of vaccine” Walter Orenstein, MD, professor and associate director at the Emory Vaccine Center, said in a press call.
Regardless of the interval, it's best to be up-to-date with your vaccinations, even if you have some extra protection due to infection. Recent data from Qatar suggests that people who have received three doses of vaccine and had a prior COVID-19 infection are best protected against being sick from COVID-19 again.
The CDC recommends waiting at least two months since your last dose of vaccine or recovery from infection to get the updated booster shot. Prior to this rollout, the CDC said adults should wait five months between their primary mRNA series and the first booster.
While the shorter interval may be safe, a longer interval may allow your body to build a more lasting immune response. Waiting for four to six months after your last dose of vaccine may be ideal for gaining long-term protection, Andrew Pekosz, PhD, a virologist and vice chair of the department of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health, said in a press call.
Moderna and Pfizer haven’t collected data on how effective it is to get a bivalent booster shot that doesn’t correspond with your primary series.
However, clinical studies on primary regimens and the initial boosters suggest that getting a mixture of the two mRNA vaccines could be even more effective than getting all the shots from the same manufacturer.
Edwards, the infectious disease expert at Vanderbilt, said mixing and matching your vaccine types likely provides the broadest immunity. Ultimately, you should get whichever updated booster is available to you.
The upcoming flu season coincides with the bivalent booster rollout. Health experts say people can streamline their vaccine appointments by getting both the flu and booster shots at the same time.
The CDC recommends that people get the shots in different limbs. Ashish Jha, MD, MPH, White House Coronavirus Response Coordinator, said getting both vaccines at the same time may cause similar or only slightly higher incidence of side effects, but no serious adverse outcomes.
“I really believe this is why God gave us two arms—one for the flu shot and the other one for the COVID shot,” Jha said in a press briefing.
The flu season typically starts in October or November in the U.S., though data from Australia indicates that the season may start even earlier this year.
In the White House press briefing this week, Jha said the updated boosters “will continue to remain free.” The government has already purchased 171 million doses of bivalent vaccine for this rollout, and there should be plenty of supply.
But Congress has failed to allocate additional funds for COVID-19 prevention and response. Initiatives like free COVID test kits have been halted because of insufficient funding.
"It's an important question that we need to address, either through federal funding or additional ways of funding," Pekosz said. "We don't want the cost of these vaccinations, testing, and treatment to limit the uptake of those, especially in the vulnerable populations."
It’s probably too early to know exactly what the booster timeline will look like going forward. Scientists aren’t yet sure just how long the protection from the updated boosters will last. They also can’t predict which new variants will arise and how well they will evade existing immune defenses.
It will take several months of follow-up with people who received the updated booster to know how quickly immune protection from that vaccination wanes. In the meantime, Fauci said that the White House was planning to give boosters once a year, as is done with flu shots. People with immunocompromised might expect to receive a booster more frequently.
“Looking forward with the COVID-19 pandemic, in the absence of a dramatically different variant, we likely are moving towards a path with a vaccination cadence similar to that of the annual influenza vaccine, with annual, updated COVID-19 shots matched to the currently circulating strains for most of the population,” Fauci said.
Scientists have also floated the idea of a universal vaccine that would protect against multiple COVID variants, including those that emerge in the future.
For now, getting the vaccines into arms and practicing masking and social distancing, are the best ways to protect people against COVID-19.
“Vaccine doses that remain in the vial are 0% effective. It’s not vaccines that save lives—it’s vaccinations that save lives,” Orenstein said.
The updated booster shots are now or will soon be available in locations where you can already be vaccinated, such as doctors’ offices, some health clinics, pharmacies, urgent care centers, and mobile COVID-19 vaccination sites. You can find vaccination sites near you at vaccines.gov.
The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.