Who needs a COVID-19 booster shot?

A woman in a face masks walks down a sidewalk. COVID-19 vaccines have been very good at keeping most fully vaccinated people out of the hospital. But that's not always been the story for people with weakened immune systems.

Not only do they face a higher risk of severe illness from COVID-19, but their bodies may not mount as robust of an immune response to the vaccines. That leaves them more vulnerable to breakthrough infections.

That's where booster shots come in. The Centers for Disease Control and Prevention (CDC) now recommends a third dose of mRNA vaccines for some people with weakened immune systems. Studies suggest the extra dose may help boost their protection.

Who needs a third shot?

About 3% of adults in the U.S. are moderately to severely immunocompromised. If you're one of them, CDC recommends getting a booster shot if it has been at least 28 days since your second dose of either the Pfizer or Moderna vaccine. (CDC says they don't have enough data yet to recommend a booster to people who got the Johnson & Johnson [J&J] vaccine. But they expect to know more about that soon.)

You may be eligible for a booster shot if you:

  • Are being treated for cancer.
  • Have a condition that lowers your immunity, such as advanced HIV.
  • Have had a stem cell transplant in the past two years.
  • Take high doses of steroid drugs.
  • Take other drugs that suppress your immune system, including after an organ transplant.

If you're not sure if you should get a booster shot, talk to your doctor.

What about everyone else?

While the vaccines have been effective against severe illness so far, there is some concern that their protection may fade over time. So CDC also recommends a third booster shot of Pfizer's vaccine if it's been at least six months since your first series and you:

  • Live in a long-term care setting.
  • Are 65 or older.
  • Are 50 to 64 years old with underlying medical conditions.

A booster shot may also be right for people:

  • 18 to 49 years old with underlying medical conditions.
  • 18 to 64 years old who are at increased risk because of where they work or live.

If you have questions about what's right for you, talk with your doctor.

These recommendations do not apply to people who got the Moderna or Johnson & Johnson vaccine. But experts expect to offer more guidance on those vaccines soon.

You can learn more about all three vaccines in our Coronavirus topic center.

Reviewed 9/27/2021

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