VERIFY Fact Sheet: COVID-19 booster shots

When should you get a COVID booster shot? How many shots are recommended? Here’s what you need to know about boosters.
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Experts and public health agencies, including the Centers for Disease Control and Prevention (CDC), are recommending COVID-19 booster shots for fully vaccinated individuals as the highly transmissible omicron variant remains dominant in the United States. 

Booster shots have prompted a lot of questions via email and text message from our VERIFY viewers, including who needs one and when, whether immunocompromised people need a third vaccine dose followed by a booster, and if otherwise healthy people need a fourth shot.

We are breaking down what we know right now about COVID-19 booster shots and additional doses. 

THE SOURCES

FAST FACTS

  • Booster vs. additional dose: People who received the Pfizer or Moderna COVID-19 vaccine should get a booster shot at least five months after getting their second dose of the vaccine, according to the CDC. The public health agency says  “moderately or severely” immunocompromised people should get an additional – or third – primary dose 28 days after their second shot before getting a fourth booster shot. 

  • What booster shots mean for the “fully vaccinated” definition: The CDC definition of fully vaccinated doesn’t include the booster shot. You are still considered fully vaccinated after your second dose in a two-shot series or two weeks after the single-dose J&J vaccine. 

  • What we know about a fourth dose for people who aren’t immunocompromised: Public health agencies are not currently recommending a fourth shot for those who are not immunocompromised, but they may recommend them in the future.   

WHAT WE KNOW

Who needs a COVID-19 booster shot and when?

If you got Pfizer or Moderna mRNA vaccines

Everyone 12 and older who received the Pfizer mRNA COVID-19 vaccine should get a booster shot at least five months after getting their second dose of the vaccine, the CDC says

Adults who received the Moderna vaccine should also get a booster shot at least five months after their second dose. 

You can mix and match brands for your booster shot or additional dose, according to Johns Hopkins Medicine. The U.S. Food and Drug Administration (FDA) has authorized Pfizer, Moderna and J&J vaccine boosters, and determined it is safe to get a booster or additional dose that is a different brand than your initial doses.

Pfizer’s vaccine and booster shot are the only ones authorized for kids and teens ages 12 to 17.

If you got the Johnson & Johnson vaccine

Those who received the one-dose Johnson & Johnson (J&J) vaccine should get a booster shot at least two months later. Pfizer or Moderna shots are preferred as that booster in most situations, according to the CDC.

Children under 12

The Pfizer vaccine and booster shot are the only ones authorized for kids and teens ages 12 to 17. Kids ages 12 and older can get the booster shot.

The FDA has authorized Pfizer’s two-dose vaccine for emergency use in children ages 5 to 11, but that does not include a booster for kids who are otherwise healthy.

Vaccines and booster shots for children under 5 have not been approved

What if you’re immunocompromised?

After completing the primary two-dose COVID-19 vaccine series, some “moderately or severely” immunocompromised people should get an additional – or third – primary dose, according to the Centers for Disease Control and Prevention and the World Health Organization (WHO).

The WHO explains that this additional dose is different from a booster and is considered part of an “extended primary series” for people who don’t develop sufficient immune protection after one or two doses of the vaccine.

Here’s who the CDC considers moderately or severely immunocompromised:

  • Receiving active cancer treatment for tumors or blood cancers
  • Received an organ transplant and are taking medicine to suppress the immune system
  • Received a stem cell transplant within the last 2 years or are taking medicine to suppress the immune system
  • Moderate or severe primary immunodeficiency (such as DiGeorge syndrome and Wiskott-Aldrich syndrome)
  • Advanced or untreated HIV infection
  • Active treatment with high-dose corticosteroids or other drugs that may suppress your immune response

The CDC says people 5 and older who fall into this category should get an additional primary shot of the Pfizer vaccine 28 days after their second shot. Those in this group who received the Moderna vaccine, which is only available to those 18 and older, should also get their additional dose 28 days after their second shot.

Immunocompromised teens 12 to 17 years old can get a Pfizer booster five months after their additional primary shot. People 18 and older can get a booster shot of either Pfizer or Moderna five months after their additional primary shot. 

No additional shot is recommended for immunocompromised people who received the one-dose Johnson & Johnson vaccine, but they can get a booster shot of the Pfizer or Moderna vaccines two months after their first shot.

People should talk to their healthcare provider about their medical condition and whether they should get an additional primary shot, the CDC says.

Are booster shots the same dose as the original vaccines?

The Pfizer and Johnson and Johnson COVID-19 booster shots use the same ingredients as the previous vaccines, the CDC says

The Moderna booster shot contains half of the original vaccine dose.  

Memorial Sloan Kettering Cancer Center writes on its website that data submitted by Moderna to the FDA and CDC shows that a half-dose booster shot “effectively strengthens a person’s immunity against COVID-19 and its variant.” Moderna also said the half-dose booster may reduce side effects.

How long should you wait to get a booster after contracting COVID-19?

If you have recovered from COVID-19 and are no longer symptomatic, you can get a booster shot, experts told VERIFY sister station WCNC. Doctors at Houston Methodist also recommend that a person waits to get a booster shot until they are out of the five-day isolation period.

There is one caveat, though. If you received monoclonal antibody treatment while sick with COVID-19, you need to wait 90 days before getting a booster shot.

How effective are booster shots?


Multiple studies have shown that booster shots help to better protect people from severe disease, hospitalization and death compared to being fully vaccinated alone, Johns Hopkins Medicine says.

One of those studies conducted from August 2021 to January 2022 was recently published in the CDC Morbidity and Mortality Weekly Report (MMWR). It found that a third mRNA vaccine dose was highly effective during the delta and omicron-predominant periods at preventing emergency department and urgent care encounters and hospitalizations associated with COVID-19.

Vaccine effectiveness during the omicron-predominant period was measured at different points after the second vaccine dose and after a third booster dose. At less than 180 days after the second mRNA vaccine dose, vaccine effectiveness against hospitalizations associated with COVID-19 was 81%. At more than 180 days after the second dose, it dropped to 57%. But after a third booster dose, vaccine effectiveness against hospitalizations improved to 90%, the study found.

Findings from a study published in the Journal of the American Medical Association in January 2022 suggest that those who have received a booster shot were better protected from both the omicron and delta variants than those who were fully vaccinated with two doses or unvaccinated.

Pfizer also said initial lab tests suggested that a booster shot of its vaccine offered more protection against omicron than just two doses of the vaccine, VERIFY previously reported.

“Although two doses of the vaccine may still offer protection against severe disease caused by the omicron strain, it’s clear from these preliminary data that protection is improved with a third dose of our vaccine,” Pfizer CEO Albert Bourla said in a news release on Dec. 8.

Are you still considered “fully vaccinated” if you haven’t received a booster shot?


Yes. The CDC says on its website that the public health agency’s definition of fully vaccinated hasn’t changed and doesn’t include the booster shot. You are still considered fully vaccinated after your second dose in a two-shot series, such as Pfizer or Moderna, or two weeks after the single-dose J&J vaccine. There is “no time limit after vaccination on your fully vaccinated status,” the Mayo Clinic says on its website.

However, those who are fully vaccinated but haven’t received a booster shot are not “optimally protected” from COVID-19, according to the CDC. A person who is “up to date” has received all recommended COVID-19 vaccines, including any booster doses when they are eligible, the public health agency says.

Will those who are not immunocompromised need a second booster shot in the future?

Public health agencies are not currently recommending another booster shot for those who are not immunocompromised, but it’s unclear if those who are otherwise healthy will need a fourth dose in the future. Anthony Fauci, M.D., Director of the National Institute of Allergy and Infectious Diseases and the Chief Medical Advisor to the President, says a fourth dose for others is possible and could be based on multiple factors.

“For example, there may be the need for yet again another boost — in this case, a fourth-dose boost for an individual receiving the mRNA — that could be based on age, as well as underlying conditions,” Fauci said during a White House COVID-19 response team press briefing on Feb. 9. “So, I don’t think you’re going to be hearing, if you do, any kind of recommendations that would be across the board for everyone. It very likely will take into account what subset of people have a diminished, or not, protection against the important parameters such as hospitalization.”

Do you have questions about booster shots? Send the VERIFY team an email to questions@verifythis.com

More from VERIFY: No, Dr. Fauci did not tell Mark Zuckerberg the COVID-19 vaccine would make people worse

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