Effect of timely immunizations on infection-related outcomes after CLL-directed treatment.

Abstract

e19032 Background: Patients with Chronic Lymphocytic Leukemia (CLL) are at a higher risk of developing infections due to disease related hypogammaglobulinemia, T cell dysfunction, neutropenia and the immunosuppressive effects of therapy. Data about mitigating infection risk with optimal vaccinations before treatment commences in CLL patients is sparse. Our study aims to evaluate the effect of pre-treatment vaccination on infection rates following therapy in patients with CLL. Methods: We performed a retrospective study across a large, multi-hospital healthcare system. The electronic health records were queried using ICD-10 codes to identify patients with CLL spanning a 10-year period between 1/1/2015 and 12/31/2024. Patients over 18 years of age who had a verifiable CLL diagnosis, longitudinal follow-up, and immunization records were included in the study. The primary outcome studied was the effect of pre-treatment vaccination status on post-treatment infection outcomes. Results: A total of 783 patients with CLL were identified, data were verified and were included in the analysis. 167 (21%) of these patients received treatment for CLL. 28 (17%) patients received chemoimmunotherapy, 56 (34%) patients received Venetoclax based therapy and 98 (59%) patients received a Bruton Tyrosine Kinase Inhibitor. Prior to treatment, 126/167 (75.4%) patients received influenza vaccination, 109/167 (65.3%) received pneumococcal vaccination, 83/167 (49.7%) received COVID-19 vaccination, and 73 (43.7%) received at least one dose of zoster vaccination. Overall, 25 (14.9%) vaccinated patients developed infections after starting therapy. 10/14 (71.4%) COVID infections occurred in those who had not received COVID vaccination prior to treatment while 4/14 (28.6%) occurred in those who had received COVID vaccine prior to treatment. Of the 14 patients who developed pneumonia, 10 had received pre-treatment pneumococcal vaccination while 4 had not received pneumococcal vaccination. Of the 3 shingles cases, 2 occurred in patients unvaccinated for shingles and one occurred in a vaccinated patient. Conclusions: Pre-treatment vaccination in CLL patients reduces risk of developing post treatment infection when compared to unvaccinated patients undergoing CLL therapy. Majority of patients who did not receive COVID vaccination prior to CLL therapy developed COVID infections after starting CLL therapy. Updating age-appropriate vaccinations prior to commencing CLL directed therapy is optimal.