The role of vaccines in mitigating the significant morbidity and mortality associated with infections in chronic lymphocytic leukemia (CLL) is a developing field of study, punctuated by the advent of novel therapeutic agents and pressing questions regarding the global SARS–CoV-2 vaccination efforts. Patients with CLL suffer from impaired innate and adaptive immunity, with functional defects in T cells, natural killer cells, and humoral response, leading to abrogated vaccine efficacy.1,2
The recently published study by Mauro et al3 in Leukemia—also reviewed in this issue of The ASCO Post—elucidates key themes for assessing immune response to the conjugate pneumococcal vaccine (PCV13) in patients with CLL.
Raamis Khwaja, MD
Philip A. Thompson, MBBS (Hons)
Nitin Jain, MD
Study Findings and Clinical Questions
In a prospective study conducted at four hematology institutions in Italy, Mauro and colleagues investigated immune response to a single dose of PCV13 vaccine in 112 patients with CLL. When measured 3 and 6 weeks after vaccination, just 9 of 112 (8%) met the criteria for serologic response (defined as a twofold increase in the pneumococcal IgG levels), including 8 of 22 (36%) previously untreated patients with CLL and 1 of 11 (9%) patients on front-line ibrutinib therapy. Notably, none of the patients who had received prior chemoimmunotherapy (fludarabine, cyclophosphamide, and rituximab, n = 32; bendamustine and rituximab, n =13) or patients with IgG levels less than 400 mg/dL (n = 26) had a serologic response. Additionally, patients aged ≥ 60 years and those with signs of disease progression had lower serologic response. This study concluded that PCV13 vaccination should be offered to patients with CLL in the early stage of the disease, preferably at diagnosis, when they have a better chance of mounting an immune response.
Several previous studies have explored the question of immune response to PCV13 vaccine in patients with CLL. In a randomized study from the Swedish CLL group, 128 previously untreated patients with CLL received PCV13 vaccine (n = 63) or the polysaccharide pneumococcal vaccine (PPSV23; n = 65).4 A total of 12 serotype-specific IgG antibodies common to both vaccines were measured at baseline and at 1 and 6 months after the vaccination. Results demonstrated a more robust response for PCV13 vs PPSV23: 40% vs 21% at 1 month and 33% vs 17% at 6 months, respectively.
Another study evaluated antibody response to PCV13 in 24 previously untreated patients with CLL compared with 15 healthy control subjects.5 Adequate serologic response was noted in 58% of patients with CLL and 100% of the control group 1 month after vaccination. The comparatively higher response rate noted in patients with CLL in this study may be reflective of early-stage disease.
As Bruton’s tyrosine kinase (BTK) inhibitors have now become standard therapy for CLL, Andrick and colleagues measured antibody response in four patients with CLL receiving ibrutinib vs four patients with CLL who were not receiving ibrutinib (control group).6 None of the patients on ibrutinib therapy mounted a serologic response, whereas all four patients in the control group met the response criteria.
Interestingly, a study evaluating early administration of ibrutinib in asymptomatic, previously untreated patients with high-risk CLL noted improved efficacy of PCV13 when patients started ibrutinib at the same time.7 The antibody response waned after 12 months, indicating a possible benefit of revaccination to boost titers. Congruent to the findings by Mauro et al, these studies highlight that advanced disease seems to dampen serologic response to the PCV13 vaccine and stress the importance of vaccination earlier in the disease course, especially prior to the initiation of anti-CLL therapy.
The Advisory Committee on Immunization Practices (ACIP) recommends that adults with immunocompromising conditions (such as CLL) should receive a dose of PCV13 first, followed by a dose of PPSV23 at least 8 weeks later.8 A second PPSV23 dose is recommended 5 years after the first PPSV23 dose. Similar to the ACIP guidelines, the European Conference on Infections in Leukemia (ECIL) consortium recommends one dose of PCV13 followed by PPSV23 after 8 weeks.9 Additionally, the guidelines advocated vaccination prior to the start of therapy, in accordance with the studies previously mentioned that showed improved response rates in treatment-naive patients. Notably, the National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines in Oncology for CLL recommend PPSV23 every 5 years (no recommendation provided for PCV13).10
Similar to the low rates of immune response to the pneumococcal vaccine, low rates of vaccine response to the influenza vaccine have been noted in patients with CLL, with response rates ranging from 7% to 26% for those receiving BTK inhibitor therapy.11,12 A recent study investigated humoral response to the adjuvant hepatitis B (HepB-CpG) and recombinant zoster (RZV) vaccines for previously untreated patients with CLL vs those receiving BTK inhibitor therapy.13 Only 4% of patients receiving BTK inhibitor therapy developed a serologic response to the HepB-CpG vaccine, compared with 28% of previously untreated patients, suggestive of an impaired de novo immune response. In contrast, there was no significant difference in response to the RZV vaccine between those who did and did not receive BTK inhibitors, attributed to the recall antigenic response from prior pathogenic exposure.
COVID-19 Vaccination and CLL
These findings have important implications for the immune response to the novel mRNA vaccines for SARS–CoV-2 for patients with CLL. Current data indicate reduced efficacy of mRNA vaccines for COVID-19 in these patients. One study evaluated 167 patients with CLL who received BNT162b2 mRNA COVID-19 vaccine and noted an antibody response rate of 39.5% (55% among those with previously untreated CLL); only 8 of 50 patients (16%) who were receiving a BTK inhibitor had an antibody response.14 Moreover, none of the 22 patients who had received anti-CD20 antibodies within 12 months of vaccination mounted an immune response.
Given suboptimal response to COVID-19 vaccines, there is a need to measure postvaccine serologic responses in patients with CLL to truly evaluate vaccine-conferred protection.— Raamis Khwaja, MD; Philip A. Thompson, MBBS (Hons); and Nitin Jain, MD
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In another study, 44 patients with CLL were evaluated for serologic response to mRNA (BNT162b2 or mRNA-1273) vaccination; 52% of the patients produced a serologic response, with a higher proportion of treatment-naive vs treated patients (17/18 = 94% vs 6/26 = 23%), including a lower proportion of patients treated with a BTK inhibitor (3/14 = 21%) or venetoclax (0/7 = 0%).15 Given suboptimal response to the COVID-19 vaccines, there is a need to measure postvaccine serologic responses in patients with CLL to truly evaluate vaccine-conferred protection. This is being investigated in several multicenter trials at this time.
Closing Thoughts
The results reported by Mauro and colleagues and additional studies summarized here suggest impaired vaccine immune response in patients with CLL, especially those receiving active therapy. Efforts should be made to administer the vaccines earlier in the disease course. Additional work is needed to evaluate other strategies (eg, booster vaccinations) where feasible in patients with CLL and other immunocompromised states.
Dr. Khwaja works in the Department of Internal Medicine at The University of Texas Health Science Center, Houston. Dr. Thompson works in the Department of Leukemia at The University of Texas MD Anderson Cancer Center. Dr. Jain works in the Department of Leukemia at The University of Texas MD Anderson Cancer Center.
DISCLOSURE: Dr. Khwaja reported no conflicts of interest. Dr. Thompson has received honoraria from and served as a consultant or advisor to Janssen, Adaptive Biotechnologies, and AbbVie; and has received institutional research funding from AbbVie, Pharmacyclics, Genentech, and Adaptive Biotechnologies. Dr. Jain has received honoraria from and served as a consultant or advisor to AbbVie/Genentech, Adaptive Biotechnologies, ADC Therapeutics, AstraZeneca/MedImmune, BeiGene, Bristol Myers Squibb/Celgene, Cellectis, Janssen, Pharmacyclics, Precision Biosciences, Servier, and TG Therapeutics; and has received institutional research funding from AbbVie, Adaptive Biotechnologies, ADC Therapeutics, Aprea Therapeutics, AstraZeneca/MedImmune, Bristol Myers Squibb, Celgene, Cellectis, Fate Therapeutics, Genentech/Roche, Incyte, Kite, Pfizer, Pharmacyclics, Precision Biosciences, and Servier.
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