The antibody-mediated response to the BNT162b2 COVID-19 vaccine was “markedly impaired” in patients with chronic lymphocytic leukemia (CLL), researchers reported in Blood.

BNT162b2, developed by Pfizer and BioNTech, is a lipid nanoparticle–encapsulated, mRNA-based COVID-19 vaccine encoding the full-length S protein of SARS-CoV-2. The vaccine showed 95% efficacy in preventing symptomatic SARS-CoV-2 infection in a phase 3 trial, but hematology and oncology patients were excluded from this trial.

Researchers initiated a prospective study ( Identifier: NCT04746092) to investigate the efficacy of BNT162b2 in patients with CLL/small lymphocytic lymphoma (SLL).

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The study enrolled 167 patients with CLL/SLL and 52 age- and sex-matched healthy control individuals. The median age of the CLL/SLL patients was 71 years, and 67.1% were men.

The disease and treatment status of the CLL/SLL patients was heterogeneous — 34.7% were treatment-naive, 44.9% were on therapy, 14.4% were in remission, and 6.0% were off therapy and had relapsed disease.

The serologic response to vaccination was evaluated after a 2-dose regimen of BNT162b2 given 21 days apart. The primary endpoint was the proportion of individuals with anti-SARS-CoV-2S antibodies.

A comparative analysis between 52 CLL/SLL patients and 52 healthy individuals showed a significantly reduced response rate among CLL/SLL patients — 52% and 100%, respectively (adjusted odds ratio [OR], 0.010; P <.001). The CLL/SLL patients had reduced antibody titers as well (median, 0.824 U/mL and 1084 U/mL, respectively; P <.001).

The antibody response rate and antibody levels were highest among CLL/SLL patients who retained a response after treatment (79.2%; median, 297.6 U/mL), followed by treatment-naive patients (55.2%, median, 1.7 U/mL), and patients who were receiving treatment at vaccination (16.0%; median, 0.4 U/mL).

Although the treatment-naive CLL/SLL patients had a significantly higher response rate and median antibody level than actively treated CLL/SLL patients (P <.001 for both), the antibody responses and antibody titers were much lower in the treatment-naive CLL/SLL patients than in healthy individuals.

The antibody response rate was 16.0% in CLL/SLL patients treated with Bruton’s tyrosine kinase inhibitors and 13.6% in patients who received venetoclax, with or without an anti-CD20 antibody.  The patients who were treated with anti-CD20 antibodies less than 12 months before vaccination failed to respond.

Based on these results, the study authors strongly recommended that “…vaccinated patients with CLL should continue to adhere to masking, social distancing, and vaccination of their close contacts. Serological tests after the second injection of the COVID-19 vaccine can provide valuable information to the individual patient and perhaps may be integrated in future clinical decisions.”

Disclosures: This research was supported by Tel-Aviv Sourasky Medical Center. Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.


Herishanu Y, Avivi I, Aharon A, et al. Efficacy of the BNT162b2 mRNA COVID-19 vaccine in patients with chronic lymphocytic leukemia. Blood. Published online April 16, 2021. doi:10.1182/blood.2021011568