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Third dose of COVID-19 vaccine: What cancer patients should know

Washington University surgeon Ryan Fields, MD, delivers the COVID-19 vaccine to a colleague. Photo by Matt Miller Washington University surgeon Ryan Fields, MD, delivers the COVID-19 vaccine to a colleague. Photo by Matt Miller

The U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) have recommended a third dose of the COVID-19 vaccine for individuals who are moderately to severely immunocompromised. Oncologists at Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine offer the following related information for cancer patients.

What is the recommendation?

The FDA and CDC have recommended an additional dose of the Pfizer-BioNTech or Moderna COVID-19 vaccine for people who:

  • Previously received two doses of either vaccine, and
  • Are moderately to severely immunocompromised – that is, those who have a moderately to severely weakened immune system

The Pfizer-BioNTech and Moderna vaccines both are called messenger RNA, or mRNA, vaccines. At this time, no additional shot has been recommended for individuals who received the single-dose Johnson & Johnson vaccine, which is a different type of vaccine called an adenovirus vector vaccine.

How does this affect cancer patients, specifically?

In the case of cancer patients, the CDC specifically recommends a third dose for those who:

  • Are actively undergoing cancer treatment for tumors or cancers of the blood, or have completed treatments within the past six months
  • Are now undergoing CAR-T cell therapy
  • Have received a bone marrow/stem cell transplant within the past two years
  • Currently are taking immunosuppressive drugs (for example, transplant-related immunosuppressive medications, high-dose steroids, alkylating agents, antimetabolites and tumor-necrosis factor, or TNF, blockers) or are receiving rituximab or another immunosuppressive biologic agent
  • Have completed immunosuppressive therapy within the past six months

Patients who previously received the two-dose Pfizer-BioNTech or Moderna COVID-19 vaccine series and later developed COVID-19 are likely protected for the next 90 days but can receive a third dose any time after they have recovered and are out of isolation.  Anyone who received monoclonal antibody treatment for COVID-19 infection should not receive a third dose until 90 days after their infusion.

Patients who have questions about the state of their immune system and how it affects whether or not they should get a third dose of the Pfizer-BioNTech or Moderna COVID-19 vaccine should contact their physician’s office.

Is there any other guidance for patients to consider?

Washington University oncologists at Siteman recommend a third dose of the Pfizer-BioNTech or Moderna COVID-19 vaccine for patients who:

  • Are in active treatment for a solid tumor cancer or hematologic cancer, which occurs in blood-forming tissue, such as bone marrow, or in the cells of the immune system
  • Received a solid-organ transplant and are taking immunosuppressive therapy
  • Received CAR-T cell or hematopoietic stem cell transplant within the last five years or are currently using immunosuppressive drugs. Patients who received a hematopoietic stem cell transplant should wait until 100 days after their transplant to be vaccinated.
  • Are being treated for chronic lymphocytic leukemia (CLL)
  • Have a moderate or severe primary immunodeficiency (for example, those with DiGeorge syndrome or Wiskott-Aldrich syndrome)
  • Have an advanced or untreated HIV infection (CD4 <200)
  • Are being treated with:
    • High-dose corticosteroids (for example, 20 or more milligrams of prednisone or equivalent per day) for at least two weeks
    • Chemotherapy
    • Tumor necrosis factor (TNF) blockers (for example, Remicade/infliximab, Humira/adalimumab or Enbrel/etanercept)
    • Medicines that are immunosuppressive (suppress the immune system) or otherwise immunomodulatory (change the immune system)
    • Radiation therapy

What individuals should not receive a third COVID-19 vaccine?

An additional dose of the COVID-19 vaccine is not recommended for those who:

  • Are receiving topical steroids or steroid joint injections
  • Previously received the single-dose Johnson & Johnson COVID-19 vaccine
  • Are not immunocompromised

What should qualifying patients know about receiving a third dose?

Cancer patients should work directly with their doctor to specifically time when vaccine doses should be given during the course of cancer treatment. This is important to ensure that the dose creates an adequate immune response.

For patients who meet the criteria, Washington University oncologists at Siteman offer this additional guidance:

  • Patients should be at least 28 days past their second Pfizer-BioNTech or Moderna COVID-19 vaccine to receive the third dose.
  • Whenever possible, Pfizer-BioNTech or Moderna COVID-19 vaccination doses should be given at least two weeks before immunosuppressive therapies, including for cancer treatment, begin.
  • Patients can receive booster doses through a local pharmacy or community vaccine clinic.
  • No documentation is currently required for immunocompromised patients to receive a booster.
  • When feasible, it is recommended that patients receive the same vaccine brand (Pfizer-BioNTech or Moderna) for the third dose as was used in the first and second doses. If that brand is not available, a third dose from the other brand can be administered.
  • Patients should continue precautions such as masking and social distancing.
  • It is not currently recommended that cancer patients undergo antibody testing to check antibody levels before receiving a third dose.

Why is a third COVID-19 vaccine shot recommended for certain patients?

The additional dose is recommended to improve immunity response to the initial, two-dose vaccine series of the Pfizer-BioNTech or Moderna COVID-19 vaccine. Early studies have found that immunocompromised individuals do not develop as robust of a response to the two-shot COVID-19 vaccination as the general population, overall, does.

Limited studies have found that cancer patients receiving treatments that included chemotherapy plus immunotherapy or immunotherapy plus biological therapy were found to have significantly lower levels of immunity (lower IgG antibody titer test) after receiving two doses of the Pfizer-BioNTech or Moderna vaccine. Studies also have found that 30% to 50% of these patients developed or increased the antibodies protecting them from COVID-19 after getting a third dose of the vaccine.

Is the third shot considered to be a “booster” shot?

No. Booster shots are given to “boost” an immune response that has diminished over time. That occurs with some childhood vaccines. In the case of the COVID-19 vaccine and immunocompromised individuals, the immunity response was not as robust, or as good, as it initially should have been. These individuals need more protection from the coronavirus. According to the CDC, emerging data have found that immunocompromised people who have low or no protection following the first two doses of either the Pfizer-BioNTech or Moderna vaccine may have an improved response after a third dose.

Can pediatric patients receive a third dose?

Cancer patients ages 12 and older who meet the criteria can receive the Pfizer-BioNTech vaccine. Patients ages 18 and older who meet the criteria can receive the Moderna vaccine.

What other important things should patients know about the COVID-19 vaccine?

There is some evidence that vaccination with mRNA vaccines prior to imaging may cause difficulties in the interpretation of the resulting images. This would not affect anything within the patient’s body. These multidisciplinary groups have published information on imaging as it relates to COVID-19 vaccination:

Sources and References

Washington University oncologists at Siteman and an infection prevention specialist at Washington University and BJC HealthCare have provided information for and reviewed this guidance. Additional sources and references are listed below.