by Dr. C.H. Weaver M.D. 4/17/2021

Because clinical trials of COVID-19 vaccines did not include patients with blood cancers and patients with these cancers are at high risk of severe illness and complications from the virus, there is great interest in understanding the effectiveness of vaccines in these groups of patients. Two new studies published in the medical journal Blood suggest that the mRNA COVID-19 vaccine has reduced effectiveness in individuals with chronic lymphocytic leukemia (CLL) and multiple myeloma, two types of blood cancer. Overall, the response rate to the vaccine was significantly less than reported for the general population and this is most likely attributed to the presence of cancer itself and certain treatments that suppress the immune system. (1,2)

Researchers compared 167 patients with CLL to 53 healthy individuals who received two doses of BNT162b2 messenger RNA (Pfizer) COVID-19 vaccine 21 days apart between December 2020 through February 2021. Antibody titers were also measured two weeks after the second dose. The researchers report that people with CLL had significantly lower immune response rates to the two-dose mRNA COVID-19 vaccine compared to healthy individuals of the same age. Only 40% of patients had a positive antibody-mediated response to the vaccine. There were however wide variations in immune response based on where patients were in their cancer treatment.

  • Patients undergoing active cancer treatment had significantly lower response rates to the vaccine when compared with people who had completed treatment and were in remission, 16% vs 79% respectively.
  • Treatment naïve patients had a 55.5% response rate and response to the vaccine was higher in people who completed CLL treatment at least a year before vaccination compared with those who were still in treatment within the last year, 94% vs 50%, respectively.
  • Low response rates among patients who were receiving treatment with Bruton’s tyrosine kinase (BTK) inhibitors (ibrutinib or acalabrutinib) or a combination of venetoclax with anti-CD20 antibodies such as rituximab were reported. No patients who received anti-CD20 antibodies within 12 months of COVID-19 vaccination responded.
  • Patients with CLL also had lower antibody titers, which tells us that, in addition to fewer patients responding to the vaccine, the intensity of the response was also lower.

Although the evaluation was performed in individuals receiving the BNT162b2 messenger RNA Pfizer vaccine there is no reason to believe the same trends would not be expected with the Moderna mRNA vaccine. The results of the study are generalizable to patients with non-hodgkin lymphoma as well which is a similar B cell cancer managed with the same immunosuppressive medications.

People with CLL and other blood cancers remain at high risk for severe illness with COVID-19 infection. Although vaccine response rates are low, vaccination against COVID-19 remains strongly recommended. Optimal vaccine timing would be before beginning treatment although this is obviously not an option for all patients. An additional booster dose of the vaccine might also be beneficial after completion of therapy, although this will need to be studied. It remains important for individuals with CLL, myeloma and lymphomas to continue to take precautions which include wearing a mask, avoiding crowds, keeping a social distance and being sure close contacts get vaccinated against COVID-19.


  1. Efficacy of the BNT162b2 mRNA COVID-19 Vaccine in Patients with Chronic Lymphocytic Leukemia
  2. Low Neutralizing Antibody Responses Against SARS-CoV-2 in Elderly Myeloma Patients After the First BNT162b2 Vaccine Dose