COVID-19 Booster Shots for Most Cancer Patients: What to Know

The U.S. Centers for Disease Control and Prevention (CDC) now recommend a third shot of the COVID-19 vaccine if you are being treated for cancer and have already received two doses of the Pfizer-BioNTech or Moderna COVID-19 vaccines.  

Under the new CDC recommendation, people who are moderately to severely immunocompromised should get another dose. This means that most Dana-Farber patients who are currently being treated for cancer should get a third shot, including people who:

  • Are actively being treated for cancer  
  • Have received CAR-T cell therapy within the last 2 years 
  • Have received a stem cell transplant within the last 2 years or are taking medicine to suppress the immune system after a stem cell transplant 
  • Are taking other drugs that may suppress the immune response (for example, biologic agents that are immunosuppressive, such as rituximab, and tumor-necrosis blockers) 
  • Are taking high-dose corticosteroids 
  • Have received a solid organ transplant 
  • Have moderate or severe primary immunodeficiency 
  • Have an advanced or untreated HIV infection   

When will a third shot be available to me?

  • Dana-Farber has started inviting eligible patients to schedule a third vaccine doses. View this webpage for more information.
  • Community locations, such as CVS and Walgreens pharmacies, offer third doses for eligible patients. You do not need a doctor’s note to get your third dose at one of these locations. Find one near you at or
Dana-Farber staff member holding a COVID-19 vaccine.

Why should you get a third shot?  

Research shows that people being treated for cancers such as leukemia, lymphoma, or multiple myeloma are more likely to get very sick if they get COVID-19. They may also have a longer illness. Data suggests that a third dose of the Pfizer or Moderna COVID-19 vaccines may provide more protection against these risks.  

Do I need a note from my doctor?  

No. When you sign up for a third shot, you will need to attest that you are immunocompromised, but you do not need a doctor’s note to get another dose.  

Should I get the same vaccine I got for the first two doses?  

Yes, you should try to get the same type of vaccine that you got for your first two doses. But it is OK to get the other vaccine if your type is not available. So, for example, if you got the Moderna vaccine for your first two doses, it is OK to get a Pfizer booster if Moderna is not available.  

  • Do not get the Johnson & Johnson/Janssen vaccine as a booster dose.  
  • Do not get more than three doses of either the Pfizer or Moderna vaccines. 

What if I got the Johnson & Johnson/Janssen vaccine?  

We do not yet know if you need a third dose after getting the Johnson & Johnson vaccine. We are hopeful that the CDC and other experts will provide guidance on this soon. 

When should I get a third dose of vaccine?  

The CDC recommends that you get the third dose at least 28 days after your second dose of vaccine.  

If you are not already fully vaccinated, we strongly encourage you to get the COVID-19 vaccine to protect yourself and your loved ones. Find a location near you at or  

Is there a difference between a third shot of the Pfizer-BioNTech or Moderna vaccines and a “booster” shot?

These third doses of Pfizer and Moderna will be considered part of the initial vaccination series for people who have not mounted an adequate immune response. A booster dose is something different. It helps refresh a waning immune response, or helps the body fight an evolving pathogen.

Due to an overwhelming number of messages and calls, we are experiencing significant delays and we may not be able to individually respond to your questions regarding third-dose COVID-19 vaccinations at this time. We know this is frustrating, and we appreciate your understanding. All of the questions we are able to answer will be updated on this blog and on this webpage.