What to Know: Total Number of COVID-19 Vaccine Doses Needed for Some People With Cancer and Those With Weakened Immune Systems — Including Second Booster Dose

Patient receives a COVID-19 vaccine

People with cancer should get more COVID-19 vaccine doses than the general public.

Memorial Sloan Kettering Cancer Center (MSK) and the Centers for Disease Control and Prevention (CDC) recommend that some people with cancer get an additional COVID-19 vaccine dose as part of their standard vaccination series, as well as a second booster dose. That’s because cancer and its treatment can severely weaken the immune system, and the standard vaccination series and single booster shot might not be enough to protect you.

  • If you initially received the Pfizer-BioNTech (Comirnaty®) vaccine or Moderna (Spikevax™) vaccine, this means you may need up to 5 total doses.
  • If you initially received the Johnson & Johnson/Janssen (J&J) vaccine, this means you may need up to 4 total doses.

Mini Kamboj, MSK’s Chief Medical Epidemiologist, explains who is eligible, timing for your doses, and how to schedule an appointment.

This information is for people with weakened immune systems (called immunocompromised).

Booster shots are recommended for everyone age 5 and older. People age 50 and older should get a second booster shot. If you are not immunocompromised, read more about how many doses you should receive and when »

Who Should Get an Additional Primary Dose and a Second Booster Shot

The CDC says that people who are “moderately to severely immunocompromised” should get more doses than the general public, including a second booster dose.

For people with cancer, this includes:

  • People with blood cancer.
  • People who are actively being treated for solid tumors with chemotherapy — and some people being treated with immunotherapy.
  • People without a functioning spleen (called asplenia).
  • People who have undergone a stem cell transplant or received CAR T therapy within the past two years.
  • People who are actively being treated for graft-versus-host-disease (GVHD) with immunosuppressive drugs (for example, sirolimus or Rapamune®).
  • People with primary immunodeficiency disorders (for example, DiGeorge syndrome, Wiskott-Aldrich syndrome).
  • People with active or untreated HIV infection.
  • People actively using high-dose steroids (for example, 20mg of prednisone or more per day for at least 2 weeks).
  • People actively being treated for an immune-related disease (for example, rheumatoid arthritis, Crohn’s disease, or psoriasis) with a tumor necrosis factor (TNF) inhibitor (for example, adalimumab or Humira®).

These eligibility criteria cover the most common situations. If you are receiving another treatment that has weakened your immune system, your doctor will be able to advise whether an additional vaccine dose as part of your standard series plus a second booster shot will benefit you.

Timing: When You Should Get Your Vaccine Doses if You Are Immunocompromised

The schedule of when to get your 2nd, 3rd, 4th, and 5th doses varies based on what brand of vaccine you get.

Pfizer Vaccine (Age 6 Months Through 4 Years)

1st dose

2nd dose — This dose should be given 3 weeks (21 days) after a child’s first dose.

3rd dose — This must be given at least 8 weeks after a child’s second dose, and it must be a Pfizer shot.

Moderna Vaccine (Age 6 Months Through 5 Years)

1st dose

2nd dose — This dose should be given 4 weeks (28 days) after a child’s first dose.

3rd dose — This dose should be given at least 4 weeks (28 days) after a child’s second dose.

Pfizer-BioNTech Vaccine (Age 5 Years Through 11 Years)

1st dose

2nd dose — This must be given 3 weeks (21 days) after a child’s first dose, and it must be a Pfizer shot.

3rd dose — This must be given at least 4 weeks (28 days) after a child’s second dose. This must be a Pfizer shot.

4th dose — This is called a “booster dose,” and it should be given at least 3 months after a child’s third dose.

Pfizer-BioNTech Vaccine (Age 12 and Older)

1st dose

2nd dose — This must be given 3 weeks (21 days) after your first dose, and it must be a Pfizer shot.

3rd dose — This is your “additional dose,” and it should be given at least 4 weeks (28 days) after your second dose. This must be a Pfizer shot.

4th dose — This is called a “booster dose,” and it should be given at least 3 months after your third dose.

5th dose — This is also a booster dose, and it should be given at least 4 months after your fourth dose (your first booster dose). Children age 12 to 17 must get a Pfizer shot as their second booster. Anyone age 18 and older can get any brand of vaccine for this dose, but Pfizer or Moderna are strongly recommended.

Moderna Vaccine (Age 18 Years and Older)

Anyone age 18 and older can get the Moderna vaccine. People who got the Moderna vaccine as their first shot should follow this schedule if they are moderately to severely immunocompromised: 

1st dose

2nd dose — This must be given 4 weeks (28 days) after your first dose, and it must be a Moderna shot.

3rd dose — This is your “additional dose,” and it should be given at least 4 weeks (28 days) after your second dose. This must be a Moderna shot.

4th dose — This is called a “booster dose,” and it should be given at least 3 months after your third dose. Pfizer or Moderna are strongly recommended for most people for this dose.

5th dose — This is also a booster dose, and it should be given at least 4 months after your fourth dose (your first booster dose). This must be a Pfizer or Moderna shot.

Johnson & Johnson/Janssen Vaccine (Age 18 Years and Older)

Anyone age 18 and older can get the J&J vaccine. People who got the J&J vaccine as their first shot should follow this schedule if they are moderately to severely immunocompromised: 

1st dose

2nd dose — This is your “additional dose,” and it should be given at least 4 weeks (28 days) after your first dose. This must be a Pfizer or Moderna shot.

3rd dose — This is called a “booster dose,” and it should be given at least 2 months after your second dose. Pfizer or Moderna is strongly recommended for most people for this dose.

4th dose — This is also a booster dose, and it should be given at least 4 months after your third dose (your first booster dose). This must be a Pfizer or Moderna shot.

Note: People who got the J&J vaccine as their first shot only need a total of 4 vaccine doses at this time.

Additional Dose and Booster Dose Side Effects

The side effects from an additional COVID-19 vaccine dose or any booster dose are similar to those experienced after receiving the initial vaccine(s). You could experience soreness at the injection site, fatigue, headache, body aches, and fever. These symptoms don’t last long — about 1 to 3 days.

Revaccination After Certain Treatments

Certain cancer treatments can completely or partially wipe out a patient’s immune system. Because of this, anything that your immune system learned before cancer treatment now may be completely gone. Your immune system needs to relearn how to fight COVID-19.

If you received any COVID-19 vaccine shots before, during, or shortly after cancer treatment, you may need to be revaccinated if your doctor thinks your immune system has recovered enough to respond to the vaccines. All age groups that are currently eligible to be vaccinated are also eligible to be revaccinated if they meet the below criteria.

You may need to be revaccinated if you received any of these treatments:

  • Hematopoietic cell transplantation (also called a bone marrow transplantation or stem cell transplantation)
  • CAR T therapy
  • Treatment with B cell depleting drugs such as rituximab or Rituxan®

Your healthcare team will determine whether you should be revaccinated and the best time to get the shots. Only healthcare providers can order revaccination for their patients after careful evaluation of eligibility. If you think you meet any of the 3 criteria for revaccination, you should talk to your healthcare team.

How Else to Protect Yourself

Even after the additional dose, people who are immunocompromised must take precautions to protect themselves from COVID-19. You should:

  • Wear a mask indoors and outdoors when you are around anyone you don’t live with.
  • Wash your hands frequently for at least 20 seconds.
  • Stay 6 feet apart from others you don’t live with.
  • Avoid crowds and poorly ventilated indoor spaces.
  • Encourage your close friends, family members, neighbors, and co-workers to be vaccinated.

If you develop symptoms of COVID-19, contact your clinical care team and get tested. Learn more about testing »

Getting Vaccinated at MSK

Adults can schedule their vaccinations at MSK by using this link.

A parent or guardian of a pediatric patient must call their child’s primary doctor at MSK to schedule a vaccination appointment.

If you have questions about an additional shot or a second booster dose, please call your MSK doctor’s office.

Please bring your CDC-issued COVID-19 vaccine card to all vaccination appointments. This is important for us to confirm the date and brand of your doses.

MSK is offering vaccinations at the David H. Koch Center for Cancer Care at Memorial Sloan Kettering Cancer Center, located at 530 East 74th Street.

We are also scheduling appointments at:

  • MSK Westchester, located at 500 Westchester Avenue in West Harrison, New York.
  • MSK Nassau, located at 1101 Hempstead Turnpike in Uniondale, New York.
  • MSK Bergen, located at 225 Summit Avenue in Montvale, New Jersey.

However, our patients don’t need to wait to get vaccinated at MSK. We encourage them to look for a vaccination location with availability near you, using the following links:


June 28, 2022


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