Patients with lymphoma or other lymphoid cancers should continue to take steps to protect themselves from COVID-19 even if they have been vaccinated against the disease, a new study by Jennifer Crombie, MD, and colleagues published in Blood Advances suggests. The study found that patients who had received anti-CD20 antibody therapy within the previous 12 months did not develop protective antibodies for COVID-19 after being vaccinated.

Jennifer Crombie, MD

“Our findings suggest that patients with lymphoid cancers who have been vaccinated for COVID-19 should not assume they have immunity against the disease,” said co-first study author Dr. Crombie, of Dana-Farber Cancer Institute. “Patients should continue to be vigilant against becoming infected.”

Study Details

The new paper reports on 23 patients with a lymphoid malignancy such as lymphoma or chronic lymphocytic leukemia (CLL) who planned to receive the Moderna or Pfizer/BioNTech COVID-19 vaccine. Both vaccines use messenger RNA, or mRNA, to trigger an immune response to the coronavirus, thereby protecting recipients from severe symptoms of COVID-19.

Seventeen of the patients who participated in the study—or 74% of the entire group—had received prior treatment for their disease. Fifteen of them had been treated with an anti-CD20 monoclonal antibody therapy such as rituximab within the previous 12 months.

Participants had their blood drawn prior to their first dose of the vaccine, at the time of their second dose, and 28 days later. The blood samples were analyzed for antibodies targeting the coronavirus responsible for COVID-19. The results were compared to those of healthy individuals who had their blood drawn at the same intervals.

Effect of Anti-CD20 Therapy

The analysis showed that none of the patients who had received anti-CD20 antibody therapy within the previous 12 months produced antibodies to the COVID-19 coronavirus by day 28 following the second dose of the vaccine.

The findings were not surprising to many researchers, Dr. Crombie remarked. The target of anti-CD20 antibodies is immune system B cells, the very cells that are involve in the production of antibodies against the coronavirus and other infectious agents.

The researchers found that the six patients who hadn’t been treated for their cancer—including five with CLL and one with marginal zone lymphoma—did develop anticoronavirus antibodies by day 28 postvaccine. Importantly, though, these patients had significantly lower antibody counts following the first dose of the vaccine than did the healthy volunteers.

The researchers also found that some patients who had received treatments other than anti-CD20 antibodies did generate an antibody response after vaccination. These included a patient with Hodgkin lymphoma who had completed a course of chemotherapy 2 months earlier, and three patients with CLL who had been treated with Bruton's tyrosine kinase inhibitors. While these results suggest that patients receiving some treatments may be able to build antibody defenses against COVID-19, the number of such patients in the current study is too small to draw a firm conclusion, Dr. Crombie stated.

Dr. Crombie added that the study focused solely on antibody production in this group of patients and did not examine whether the vaccine triggers another component of the immune response: T cells. That will be analyzed in an ongoing study that includes additional patients with lymphoid malignancies.

Until questions about the T-cell response and other aspects of the immune response to vaccination are answered, doctors continue to recommend vaccination for patients who have been treated for lymphoid malignancies, Dr. Crombie said, in the hope that the vaccines will be found to provide some protection against COVID-19.

Disclosure: For full disclosures of the study authors, visit ashpublications.org.