COVID Vaccine Boosters: What You Need to Know
Sep 28, 2021

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 third doses.

Who needs a third dose of COVID vaccine? 

A third dose is only recommended for people who are moderately or severely immunocompromised and who received two doses of either the Pfizer or Moderna mRNA vaccine. It is called a third dose, not a booster, because people who are immunocompromised need an additional dose to reach the same level of protection against COVID-19 as other people, who are not immunocompromised, achieve with two doses.

Right now, the only people who need an additional dose are people 12+ with moderately or severely weakened immune systems (ex. people who’ve had an organ transplant or are being treated for cancer) AND originally got an mRNA COVID vaccine by Pfizer or Moderna. They should get a third dose 28+ days after the second one, ideally with the same vaccine they originally received.

Who needs a COVID booster? 

For now, boosters are only recommended for some adults who received two doses of the Pfizer mRNA vaccine over six months ago. The CDC says the following people should receive a booster dose:

The CDC also says the following people may receive a booster dose if the benefits outweigh the risks for them personally, specifically:

  • Adults 18-49 who got the first two doses of the Pfizer COVID vaccine AND who have underlying conditions that increase their chances of getting seriously sick with COVID.
  • Adults 18-64 who got the first two doses of the Pfizer COVID vaccine AND who live or work somewhere that puts them at high risk of getting sick with COVID (ex. healthcare workers).
Who doesn’t need a COVID vaccine booster dose?

People who got Moderna’s or Johnson & Johnson’s COVID vaccine don’t need a booster dose yet. Those groups might end up needing boosters in the future, but right now there’s not enough science for public health experts to make that call.


Have you read:

If I need a COVID vaccine booster or a third dose, when should I get it?

If you have a moderately or severely weakened immune system AND got an mRNA vaccine, you need a third dose 28+ days after the second.

If you aren’t immunocompromised, got the Pfizer vaccine, AND are in one of the groups mentioned above, you should get a booster dose at least 6 months after the second.

Why are booster doses necessary?

COVID vaccines work really well, but they aren’t perfect. And it looks like protection from them might be going down over time, especially for people over 65. Another dose might help provide a little extra protection for people who are at higher risk of getting seriously sick with COVID.

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

Yes. You’re still considered fully vaccinated if you got the first two doses of either Pfizer’s or Moderna’s COVID vaccine OR the single-dose COVID vaccine by Johnson & Johnson.

Do boosters mean the original series don’t work? 

No. Immunity isn’t a light switch — something you either have or you don’t. Protection might be going down for some groups, but the vaccines still work really well at keeping vaccinated people alive and out of the hospital. Those who don’t qualify for a booster are still in better shape than if they hadn’t been vaccinated.

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.


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