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FAQ: Booster vs Third Dose Eligibility

Booster or third dose?

Booster

  • Helps boost waning immunity
  • Given at least 5 months after initial Pfizer & Moderna doses or 2 months after the J&J shot
  • Approved for all adults, 5+ for Pfizer

Third dose

  • Helps certain people reach a stronger level of immunity not reached after 2 doses
  • Given 28 days after the second vaccine dose
  • For those with certain immunocompromising conditions

 

As the eligibility for the COVID-19 vaccine evolves, you may be wondering if you should get an additional dose. We answered some frequently asked questions below. 

What is the difference between a “third dose” and a “booster”?

A “third dose” of an mRNA vaccine is available to people who may not have had a strong enough immune response after receiving the first two doses. For example, those who are immunocompromised need a third dose to reach a stronger level of immunity against the virus. 

A “booster” is an additional vaccine dose given to individuals who may have waning immunity because they completed their initial vaccine series many months ago. The rise of variants is another reason why some people may be mounting a less robust immune response. 
 

Who is eligible for a third dose?

A third dose of the Pfizer or Moderna vaccine is available for people with certain immunocompromised conditions including current treatment for cancer, those who received an organ transplant or those with advanced or untreated HIV.

Visit the Centers for Disease Control and Prevention site for the latest additional dose information for immunocompromised individuals.

Who is eligible for a booster?

CDC recommends everyone stay up to date with COVID-19 vaccines for their age group.

Visit the Centers for Disease Control and Prevention site for the latest COVID vaccine eligibility requirements

Can I "mix and match" vaccines for my booster shot?

The CDC now allows for recipients to "mix and match" their booster shot. That means if your first two doses were with the Pfizer vaccine, you can receive a booster dose with the Moderna vaccine. If you received a Johnson & Johnson vaccine, you are eligible to receive a Pfizer or Moderna booster shot.

I do not have any underlying conditions. Why would I need a booster?

The available data shows people who got their initial doses of the vaccine may have waning immunity after a period of time. A booster shot can help boost protection against COVID-19.

Will I experience the same side effects for this extra dose as I did for my previous shots?

So far, reactions reported after an additional dose were similar to that of the two-dose series: fatigue and pain at injection site were the most commonly reported side effects, and overall, most symptoms were mild to moderate. However, as with the two-dose series, serious side effects are rare, but may occur.