COVID-19 Vaccine Boosters: Who Needs One and When?

Published 12:00 pm Sunday, October 24, 2021

There have been several updates lately regarding COVID vaccine boosters.

  • Pfizer and Moderna COVID vaccines require 2 doses to be considered “fully vaccinated.”
  • Johnson & Johnson COVID vaccine requires a single dose to be considered “fully vaccinated.”

But for those who are already fully vaccinated, here’s a breakdown of who should get a booster shot and when, based on the latest recommendations from the CDC on October 21.

Booster Flow Chart


Who needs two doses?

  • Anyone 18+ years old who originally got the single dose of Johnson & Johnson (also known as J&J or Janssen) vaccine should get a booster dose*, at least 2 months after the first.

* 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.  


Who needs three doses?

  • Anyone 12+ who has a moderately or severely weakened immune system who also got 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 2-dose vaccine series.
  • Anyone who is at high risk of getting seriously sick with COVID-19 who also originally got the Pfizer or Moderna vaccine, can get a booster dose* of COVID-19 vaccine, 6+ months later. These groups include:

If you don’t fit it into any of the above groups, the CDC says you don’t need another dose yet. 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.

* 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.  


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 can use any COVID-19 vaccine as a booster dose. 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 do some people need more doses of COVID-19 vaccines? 

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 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.


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.

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