COVID Vaccine Boosters: What You Need to Know
Nov 22, 2021

Note: This post has been updated to reflect the latest CDC recommendations, as of January 5, 2022. 

There’s been a lot of confusion lately over COVID vaccine boosters and third doses. What is the difference? Who needs them? When should they get them? And why are they necessary? As the pandemic continues and more research comes out, public health recommendations are evolving to ensure they’re based on the most up-to-date science. Here’s the latest on COVID vaccine boosters and, for moderately and severely immunocompromised folks, third doses in the primary series.

Who needs a booster dose?
  • Everyone 12+ is now eligible for a booster dose of COVID-19 vaccine.

Our handy booster chart is up to date with the latest recommendations:


Who needs a third dose in the primary series
  • Anyone 5+ who has a moderately or severely weakened immune system who got two doses of the Pfizer or Moderna vaccine should get a third full dose of the same vaccine, 28+ days later. This additional dose of mRNA COVID-19 vaccine should improve immunocompromised people’s response to their initial vaccine series. Note that individuals under 18 are only eligible for the Pfizer vaccine at this time.
  • After getting a third dose in the primary series, moderately and severely immunocompromised people OVER 12 should also get a booster dose after completing this primary vaccination series (5 months later).

Children ages 5-11 are eligible for the COVID-19 primary series (including third doses for those who need one), but not eligible for boosters at this time. This could change in the future as we get more data, but for now, two doses still greatly lower the chances you’ll get seriously sick with COVID.

Have you read:

Do people need to get the same vaccine they originally received when they get the booster?

That depends. Those who need a third dose because of a weakened immune system should get the same vaccine for the additional dose.

For people who don’t have a weakened immune system, but who should get a booster, the CDC says that you should get either the Pfizer or Moderna vaccine, if possible. It doesn’t need to be the same vaccine that you originally received. If you aren’t sure which vaccine would be best for you, talking to a healthcare provider can help you decide.

Why are boosters necessary?

Getting another dose could help bump up your protection against COVID-19, especially if you’re in a group that’s most at risk of getting seriously sick from the disease, protection has gone down over time, or you didn’t get strong enough protection from the original dose(s).

How safe are the booster doses?

Studies so far point to the booster dose of Pfizer and Moderna COVID-19 vaccines being just as safe as previous doses. While health officials will continue to keep a close eye on the safety of COVID-19 vaccines (including boosters), side effects don’t appear to be any more common or serious compared to previous doses.

Recently, the CDC updated their COVID-19 vaccine recommendations to recommend that Pfizer and Moderna COVID vaccines be given instead of the Janssen (also known as the Johnson & Johnson or J&J) vaccine, when possible and appropriate.

The reason for the update is due to a new analysis showing that the risk of a blood-clotting condition after the J&J vaccine is still rare but greater than previously thought. In light of the new information, the CDC did a risk-benefit analysis showing that the mRNA vaccines by Pfizer and Moderna are safer and more effective than the J&J vaccine.

If I don’t get a booster, am I still considered “fully vaccinated”? 

Yes. You’re still considered fully vaccinated if you get the first two doses of either Pfizer’s or Moderna’s COVID vaccine OR the single-dose COVID vaccine by Johnson & Johnson. However, if you are eligible for a booster but have not yet received one, you are not considered “up to date” on your COVID-19 vaccinations and should get your booster.

Does a booster mean the vaccine doesn’t work? 

Nope. It’s true that you can still get COVID-19 after being vaccinated, but all three vaccines work really well at lowering your chances of dying or landing in the hospital due to COVID-19. The extra dose simply helps dial up the protection even more for folks who maybe didn’t respond fully to the original series or whose protection is going down over time.

As researchers get more data and the virus changes over time, the number and schedule of doses for COVID-19 vaccines might need to be tweaked to give people the best protection possible against dying or being hospitalized from COVID-19. This doesn’t mean the recommendation was wrong before. It means that recommendations are based on the best available data, and that data can change over time.

Recommendations seem to be changing all the time. How can I keep up?

We get it. As we get more information about the virus and vaccinate more people, we’re having to adapt. Recommendations are based on the best science available at the time. As things change, we’ll have to too. For the latest science-based info, we recommend visiting Vaccinate Your Family.

* NOTE: Booster doses of the Pfizer or Johnson & Johnson COVID-19 vaccines are the same dosage as the original series. Moderna’s COVID-19 vaccine booster is a half dose.

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