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September 13, 2021

Most blood cancer patients benefit from a third COVID-19 shot, study shows

Treatments that suppress the immune system can reduce vaccine efficacy, but a booster can make a difference

More than 50% of patients with B-cell blood cancers produced antibodies in response to a third dose of a COVID-19 vaccine despite having no detectable antibodies after the first two doses, according to a study conducted by The Leukemia & Lymphoma Society.

Patients who had a more favorable response to the first two doses also showed increased antibody levels after the third dose, the data shows.

But blood cancer patients who received a third dose after undergoing treatment with the antibody rituximab in the previous 6-12 months did not have any detectable antibodies. Some patients on Bruton tyrosine kinase inhibitors also failed to make detectable COVID-19 antibodies.

The study examined the effects of giving booster shots of the Moderna or Pfizer-BioNTech vaccines, which each use mRNA technology. Earlier this summer, the U.S. Food and Drug Administration authorized booster shots for people who are immunocompromised. 

"The additional COVID-19 vaccine dose appears to be improving immune response in many people with blood cancer — one of many conditions that can suppress a person's immune system," said Gwen Nichols, chief medical officer at the Leukemia & Lymphoma Society. "However, while vaccination offers protection to the majority of blood cancer patients, some will not mount a full antibody response even with this additional dose."

The Leukemia & Lymphoma Society estimates that at least 100,000 blood cancer patients in the U.S. will not have detectable antibodies even after a third dose of an mRNA vaccine.

The Leukemia & Lymphoma Society recommends booster shots for blood cancer patients who received two doses of either the Moderna or Pfizer vaccines. 

No recommendations have been made about additional doses of Johnson & Johnson's COVID-19 vaccine. However, The Leukemia & Lymphoma Society says patients who have received a non-mRNA vaccine should talk to their healthcare providers about the possible benefits of an additional dose.

Current cancer treatment guidelines do not advise delaying COVID-19 vaccination in blood cancer patients who are under treatment or pausing treatments to get vaccinated.

Cancer patients are urged to get vaccinated and to continue following precautions — like wearing a mask and social distancing — to reduce the risk of infection. Previous data has shown that cancer patients have a higher risk of severe COVID-19 complications, including death, than healthy people.

Rituximab also is used to treat patients with rheumatic diseases such rheumatoid arthritis and lupus. Studies on these patients also have shown low antibody levels after the first two doses of COVID-19 vaccines.

The latest study included 49 patients with a B-cell blood cancer. Of them, 17 didn't have an antibody response after the third dose. Of the 32 patients who did, 21 of them had no initial antibody response after the first two doses, but did have detectable antibodies after the booster shot.

The study was published in the journal Cancer Cell. It expands on earlier findings from the Leukemia & Lymphoma Society National Patient Registry.

In an earlier study, patients with non-Hodgkin Lymphoma and chronic lymphocytic leukemia were less likely to have detectable antibodies after two doses of either the Moderna or Pfizer vaccines. Research has shown that these two cancers target the body's healthy B cells, which are needed to fight infections and mount antibody responses to the vaccines.

"Antibody levels in our study ranged from 2.2 to over 2,500," said Lee Greenberger, the society's chief scientific officer. "Antibodies tell us that a patient has responded to vaccination — and that is a positive finding, but vaccine experts are still working to determine exactly what antibody level is needed to protect against COVID-19 infection or its worst outcomes."

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