According to a study by the Leukemia & Lymphoma Society, 25 percent of blood cancer patients who received COVID-19 vaccinations failed to produce detectable antibodies.

Conducted between March and May, 2021, the study of more than fourteen hundred current and former blood cancer patients — the largest analysis to date to report detailed findings by blood cancer and treatment type — found that, at least two weeks after receiving their second dose of the Moderna or Pfizer mRNA vaccine, non-Hodgkin lymphoma patients were least likely to have detectable antibodies, with seronegative percentages ranging from 21 percent among patients with diffuse large B cell lymphoma to 56 percent among those with mantle cell lymphoma. Among leukemia patients, those with chronic lymphocytic leukemia (CLL) were most likely to be seronegative (36 percent), with higher rates among CLL patients who were treated within the last two years with drugs that impair B-cells. Multiple myeloma patients were more likely to have detectable antibodies compared with other blood cancer patients, with only 5 percent testing seronegative, although other studies have reported higher seronegative rates of up to 15 percent.

The study also found that six of seven patients who received CAR-T cell immunotherapy for CLL, diffuse large B cell, or follicular lymphoma were seronegative after vaccination. These low response rates are similar to another study and likely due to elimination of normal B-cells by the therapy. By contrast, four of five patients who received a different type of CAR-T for multiple myeloma produced robust antibodies. LLS experts concluded that vaccination offers protection to most blood cancer patients and should be combined with prevention precautions for best protection.

"Although some patients with hematologic malignancies will not mount a full antibody response compared to healthy individuals, vaccines are safe and offer protection to the majority of blood cancer patients," said LLS chief medical officer Gwen Nichols. "But not everyone will be protected, and blood cancer patients are at increased risk of serious illness and death from COVID-19. We encourage blood cancer patients to take every measure to protect themselves from COVID-19 by getting vaccinated and continuing to take preventative precautions. This includes wearing a mask, social distancing, and avoiding crowds and poorly ventilated indoor spaces."

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