Vaccination patterns among patients receiving ICIs: A practice-informing implementation analysis.

Abstract

e22673 Background: Vaccination is recommended for patients receiving immune checkpoint inhibitors (ICI), yet historically low vaccination rates in patients with cancer receiving cytotoxic therapy have raised concern about uptake during treatment. Emerging data suggest that vaccination during ICI therapy may confer survival benefits beyond infection prevention. We hypothesized that ICI-treated patients exhibit strong vaccine engagement but incomplete adherence to ASCO guidelines, highlighting a clinically actionable opportunity to improve preventive care. Methods: A registry-validated retrospective cohort study in a large integrated healthcare system identified patients treated with ICI between 2018-2024 and a propensity-matched cohort of healthcare-active patients without cancer to contextualize baseline vaccination rates. Vaccination status was captured from the medical record and verified against the California Immunization Registry. Uptake of ASCO-recommended vaccines was evaluated and temporally classified relative to ICI therapy. Vaccination rates and dosing patterns were compared between ICI-treated patients and matched controls. Descriptive statistics and group comparisons used chi-square, Fisher’s exact and Wilcoxon rank-sum tests. Results: In a cohort of 1859 ICI-treated patients, 75.6% were partially vaccinated in alignment with guidelines, 13.8% were fully vaccinated, and 10.7% had no documented vaccine. When compared to a matched cohort, overall vaccination rates were similar. COVID-19 vaccination rates were high and comparable between ICI-treated patients and controls (87.1% vs 85.5% p = NS), though consistent with national trends, rates declined from 2021-2024 in both groups. Notably, 59.0% of ICI-treated patients received at least one ASCO-recommended vaccine within 100 days of ICI initiation. In multivariable analysis adjusting for age and sex, older age and male sex were associated with higher odds of receiving a vaccine within 100 days of ICI initiation (age: aOR 1.01/year, 95%CI 1.01-1.02; male sex: aOR 1.09, 95%CI 1.01-1.47). Across vaccine types, pneumococcal, Tdap/Td and zoster vaccines demonstrated the lowest uptake (unvaccinated: 56.2%, 64.2%, 65.9%, respectively) and offer greatest opportunity for targeted intervention. Conclusions: Vaccination engagement among patients receiving ICI is high within a large healthcare system and is comparable with historically reported rates in patients receiving cytotoxic therapy. Vaccination rates were comparable to matched non-cancer controls, though most patients remained incompletely vaccinated according to guidelines, particularly for pneumococcal, Tdap/Td and zoster vaccines. This work highlights an opportunity to build on existing engagement by integrating systematic vaccination assessment and delivery into routine ICI care to further strengthen guideline-concordant preventive care.