Does Chemotherapy Impact COVID-19 Vaccine Protection?

More than 600 million doses of COVID-19 vaccines have been given in the United States over the past two years. These vaccines help decrease the risks of serious illness, hospitalizations, and death if you’re infected with SARS-CoV-2, the virus that causes COVID-19. However, patients receiving certain cancer treatments may not get the full protection of the vaccines.

How do COVID-19 vaccines work?

You may have heard of the different brands of COVID-19 vaccines, like Pfizer-BioNTech (also called COMIRNATY), Moderna, Johnson & Johnson (Janssen), and Novavax. These are the four approved vaccines in the United States.

These vaccines use different mechanisms to help your immune system produce COVID-19 antibodies. When your immune system detects a foreign invader, like the SARS-CoV-2 virus, it makes proteins called antibodies to help destroy the harmful invader.

Both Pfizer-BioNTech (COMIRNATY) and Moderna vaccines use messenger ribonucleic acid (mRNA). These genetic materials are created in a laboratory to help teach your immune system to recognize the COVID-19 virus. Your immune system then makes antibodies to fight the virus if you become infected later.

The Johnson & Johnson (Janssen) vaccine uses a vector virus – a modified version of a different virus – that also triggers your immune system to recognize the COVID-19 virus and create antibodies.

Novavax is a protein subunit vaccine. It’s a type of vaccine that contains harmless copies of the COVID-19 spike protein and another ingredient called an adjuvant. The adjuvant helps the immune system produce antibodies to fight future COVID-19 infections.

None of these four U.S.-approved vaccines contain a live COVID-19 virus.

Are COVID-19 vaccines less effective in people on chemotherapy?

Studies have shown that COVID-19 vaccines might not be as effective in people who are receiving cancer treatment. This was especially true for patients receiving aggressive chemotherapy and those with blood cancers like leukemia and lymphoma.

In one study, researchers at the University of Arizona Cancer Center compared the immune response of cancer patients on immunosuppressive therapy – like chemotherapy – with healthy adults after they received two doses of COVID-19 vaccines.

The researchers looked at B-cells and T-cells, which are part of the body’s defense system, and antibodies. Cancer patients had a significantly reduced antibody and T-cell response compared to the healthy participants after two doses of COVID-19 vaccines. A few cancer patients in the study had no immune response to the vaccine.

Why do COVID-19 vaccines provide less protection to cancer patients?

Some cancer treatments can weaken your immune system. For example, chemotherapy works by killing cancer cells in the body. But chemotherapy also destroys normal cells like your bone marrow cells. Damaged bone marrow cells produce fewer white blood cells (your fighter cells), which means that your immune system is weak and unable to fight infections as well as it should.

If your immune system is weak, the vaccine might not trigger your defense system to produce enough antibodies to recognize and fight future COVID-19 infections.

Certain cancer treatments, like stem cells or bone marrow transplants, can wipe out your immune system. A widely used cancer drug, rituximab, can also eliminate the antibody response to COVID-19. Because of this, any protection you had from the COVID-19 vaccines may also be completely or partially eliminated. In this case, your oncologist may recommend you get revaccinated after treatment.

Should cancer patients receive the COVID-19 vaccines?

Yes. Experts agree that the COVID-19 vaccines are safe for people with cancer. Even though some cancer patients may not receive the full immune response from the vaccine, any amount of protection is better than none.

The National Comprehensive Cancer Care Network (NCCN) and American Cancer Society (ACS) recommend all people with cancer be fully vaccinated against COVID-19. The American Society of Clinical Oncology (ASCO) states that patients who currently have cancer, are undergoing active cancer treatment, or are cancer survivors may be offered COVID-19 vaccination.

Cancer patients receiving treatment that suppresses the immune system are at higher risk for complications, hospitalization, and death if they are infected with COVID-19. That’s because a weakened immune system makes it more difficult to fight an infection like COVID-19.

Let’s say you’re an adult with a moderately or severely suppressed immune system. In that case, the CDC recommends that you follow this COVID-19 vaccine schedule:

Based on the CDC’s recommendation, people who are immunocompromised (with a weakened immune system) – including some cancer patients – should receive an additional dose of the COVID-19 vaccine.

For example, you would receive three doses of the Pfizer-BioNTech or Moderna vaccine to complete the primary series, plus an updated booster dose. For the Johnson & Johnson (Janssen) vaccine, you’d receive two doses to complete the primary series plus a booster. The extra dose of the COVID-19 vaccine is not the same as a booster dose.

Talk to your oncologist about the right timing to receive the COVID-19 vaccine. Some healthcare providers may recommend getting the vaccine between cycles of cancer therapy if you’re in the middle of treatment.

Are there any cancer patients who should not get vaccinated?

If you’re undergoing bone marrow/stem cell transplant or chimeric antigen receptor (CAR) T-cell therapy, your cancer care team may recommend delaying COVID-19 vaccination (or revaccination) until your immune system has recovered.

Even if you’re a fully vaccinated cancer patient, you should still take precautions to protect yourself from COVID-19 infection. Continue to wear a mask, social distance, avoid crowds, wash your hands, and encourage family members and caregivers to be vaccinated. Discuss special precautions and other preventive measures with your healthcare providers.