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Six Months After Second Pfizer Vaccine Dose, People With Solid Tumors Have Same COVID-19 Antibody Levels as People Without Cancer

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Six months after receiving their second dose of the Pfizer-BioNTech COVID-19 vaccine, people diagnosed with solid tumor cancers had about the same antibody levels as people who hadn’t been diagnosed with cancer, according to a study.

The research was published online on Sept. 2, 2021, by the journal Cancer Discovery. Read the abstract of “Six Month Efficacy and Toxicity Profile of BNT162b2 Vaccine in Cancer Patients with Solid Tumors.”

Doctors divide cancer into two main types: cancers that form solid tumors and cancers of the blood. Blood cancers don’t form tumors.

About the Pfizer-BioNTech COVID-19 vaccine
About the study
What this means for you

About the Pfizer-BioNTech COVID-19 vaccine

On Aug. 23, 2021, the U.S. Food and Drug Administration (FDA) granted full approval to the Pfizer-BioNTech COVID-19 vaccine. The vaccine is now marketed as Comirnaty to prevent COVID-19 in people age 16 and older. The FDA has found that this vaccine is safe and highly effective for preventing COVID-19, as well as serious illness and death from the disease.

The Pfizer vaccine continues to be available under emergency use authorization:

  • for young adults ages 12 to 15
  • as a third booster dose for certain immunocompromised people

The Pfizer-BioNTech vaccine works by using genetic material called messenger RNA (mRNA). The mRNA vaccines contain a small piece of the coronavirus’s mRNA, which tells your body to make copies of a protein in the virus called the spike protein. Your immune system then builds up immune cells and antibodies to fight the spike protein. So, if you’re exposed to the COVID-19 virus, your immune system recognizes the virus and protects you from infection.

The Moderna COVID-19 vaccine is also an mRNA vaccine.

Because mRNA is just a small piece of the virus copied in a lab, the vaccine cannot cause COVID-19 and is considered safe for people with weakened immune systems — including people who are receiving treatment for cancer.

Experts have recommended that most people who have been diagnosed with cancer or have a history of cancer should get a COVID-19 vaccine. Still, you should talk to your doctor about whether getting vaccinated is the right decision for your individual situation.

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About the study

People who are currently receiving treatment for cancer — including breast cancer — have a higher risk of severe illness if they’re diagnosed with COVID-19.

In the first studies on the effectiveness of the Pfizer-BioNTech COVID-19 vaccine, less than 4% of the people in the study had been diagnosed with cancer. It was unclear how well the vaccine would work in people receiving cancer treatment.

Later studies found that people receiving cancer treatment developed an adequate immune response after receiving the Pfizer vaccine. For this study, the researchers wanted to see if the vaccine continued to offer protection from the virus 6 months after the second dose in people receiving treatment for solid tumor cancers.

The study included 154 people diagnosed with solid tumor cancers and 135 healthcare workers of similar age who had not been diagnosed with cancer.

All the people with cancer were receiving treatment at the Rambam Health Care Campus’s oncology center in Haifa, Israel.

Of the people diagnosed with solid tumor cancers:

  • 36% had gastrointestinal cancer
  • 23% had lung cancer
  • 17% had breast cancer
  • 11% had genitourinary cancer
  • 84% had metastatic disease

Of the people diagnosed with cancer:

  • all were receiving intravenous treatments (which means the medicine is delivered directly into the bloodstream through an IV or a port)
  • 62% were receiving chemotherapy
  • 36% were receiving targeted therapy
  • 30% were receiving immunotherapy

Some of the people were receiving more than one type of treatment.

The people were receiving cancer treatment at the time of their second Pfizer vaccine dose and for 6 months afterward.

The researchers compared COVID-19 antibody levels between the two groups right after the second dose and again 6 months later. Six months after the second dose, they found:

  • 79% of the people receiving treatment for cancer had COVID-19 antibodies
  • 84% of the healthcare works who had not been diagnosed with cancer had COVID-19 antibodies

The actual levels of COVID-19 antibodies between the two groups were similar. Still, the researchers noted that antibody levels declined dramatically 6 months after the second dose in both groups.

The researchers also pointed out that only one person receiving cancer treatment was diagnosed with COVID-19 after the second dose of the Pfizer vaccine.

“In our study we saw that in all outcomes, including immunogenicity, infectivity rate throughout the six-month period, and safety, patients with solid tumors depicted a similar trend as the general population,” senior author Irit Ben-Aharon, M.D., Ph.D., director of the oncology division at Rambam Health Care Campus, said in a statement.

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What this means for you

If you’re currently receiving breast cancer treatment and are worried about how effective a COVID-19 vaccine may be for you, this study offers reassuring results.

While COVID-19 antibody levels declined in people diagnosed with cancer, it’s encouraging to know that the decline was the same as it was in people who weren’t diagnosed with cancer.

The results also suggest that getting a booster shot — a third dose of either mRNA vaccine — may be a good idea if you’re receiving breast cancer treatment.

If you have a weakened immune system from breast cancer treatment and are fully vaccinated with either the Pfizer or Moderna vaccine, the FDA and Centers for Disease Control and Prevention (CDC) have recommended you talk to your doctor about getting a booster shot. There are no recommendations yet on a booster shot for immunocompromised people who had the Johnson & Johnson (J&J) vaccine (also called the Janssen vaccine).

Visit COVID-19 Vaccine Facts for People With Breast Cancer for more information.

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Written by: Jamie DePolo, senior editor

Reviewed by: Brian Wojciechowski, M.D., medical adviser


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