COVID-19 Vaccines May Have Reduced Efficacy in People with Blood Cancers

The results of two studies indicate that the mRNA COVID-19 vaccine may have attenuated efficacy in people chronic lymphocytic leukemia (CLL). The results were published in the journal Blood.

In the first study, researchers assessed 167 patients with CLL, of which almost 40% had a positive antibody-mediated response to the COVID vaccine; the control group, comprised of health adults, showed a positive immune response.

The results showed significant variations in immune response among the population with CLL depending on their stage of treatment. For example, the researchers noted, patients undergoing active cancer treatment had appreciably lower responses to the vaccine compared with individuals in remission (16% vs. 79%). Also, treatment naïve patients had a 55.5% response rate. Moreover, the results demonstrated that response to the COVID vaccine was notably higher in patients who had completed CLL treatment at least a year before receiving the vaccine compared with individuals who were still in treatment within the last year (94% vs. 50%).

The second study comprised of 167 patients with CLL and 53 health controls. The study subjects were administered two doses of the Pfizer vaccine 21 days apart. The average age of the patients was 71 years old, and most (67%) were men. Overall, about 35% were treatment naïve, approximately 45% were on active therapy, 14.4% were previously treated, and in complete or partial remission, and 6% were in relapse. Patients were followed over an average of 75 days since receiving their first shot, and none of them developed a COVID infection in that time.

When assessing immune responses to the vaccine based on which CLL treatment patients received, the researchers observed similarly low response rates among patients who were receiving common targeted therapies, including Bruton’s tyrosine kinase (BTK) inhibitors (ibrutinib or acalabrutinib), or a combination of venetoclax with anti-CD20 antibodies such as rituximab. The researchers noted that none of the patients who received anti-CD20 antibodies within 12 months of COVID-19 vaccination responded. 

“Even though response rates were not optimal, patients with CLL should still get the vaccine and, if appropriate, it may be better to do so before CLL treatment starts although the disease itself may affect the response,” said lead author of the study Yair Herishanu, MD, associate professor in hematology and head of the CLL service at the Tel Aviv Sourasky Medical Center in Israel “Equally important is continuing to take precautions – wearing a mask, avoiding crowds, keeping a social distance, and being sure close contacts get vaccinated against COVID-19.”