Revaccination status after bone marrow transplant and chimeric antigen receptor T-cell therapy.

474 Background: Revaccination after stem cell transplant (SCT) or Chimeric Antigen Receptor T-Cell therapy (CAR-T) therapy is standard, but faces challenges due to inconsistent guidelines, immunosuppression, multiple shots and intervals, insurance coverage and vaccine hesitancy. This two-phase study aimed to assess current revaccination rates and implement strategies to improve them. Methods: In Phase I (2015–2024), revaccination records were reviewed for 429 patients who received autologous or allogeneic transplants or CAR-T therapy, excluding those who were deceased within 6 months of receiving therapy. Key secondary end points evaluated were rates of acute or chronic graft versus host disease, time to revaccination, and insurance. Results: Revaccination rates stratified by type of cellular therapy are summarized in Table 1. Rates of first dose of inactivated vaccines ranged from 57.9%-70.59% (with one outlier-Zoster at 14.6-19%) for autologous and allogenic transplant recipients. Rates for the full course dropped to 40-50% in the same group. The live-attenuated MMR vaccine was received by 6-11% of patients. The rates of revaccination in CAR T were much lower across all vaccines. Conclusions: Significant gaps in revaccination strategy remain. These have resulted in suboptimal revaccination rates, delay in initiation of revaccination, and low immunization rates of certain vaccines. Phase II of our multipronged intervention is now underway which includes development of standardized protocols, EHR-based order set, educating patients and providers, and providing an immunization card to patients to improve adherence. Vaccination rates and time to vaccination post-cellular therapy. Vaccine Transplant type Auto-SCT (n=163) Allo-SCT(n=221) CAR-T(n=45) DTaP Any dose 64.60% 70.59% 15.56% Full course 41.50% 49.77% 0.00% Time to vaccination (months) 16.7 11.9 11.1 Hep B Any dose 61.00% 67.87% 6.67% Full course 41.50% 49.32% 0.00% Time to vaccination (months) 16.6 12.0 10.7 Hib Any dose 57.90% 67.87% 11.11% Full course 40.90% 51.58% 0.00% Time to vaccination (months) 16.1 11.8 13.1 PCV Any dose 61.00% 71.04% 31.11% Full course 42.70% 52.04% 0.00% Time to vaccination (months) 19 11.6 12.1 Polio Any dose 58.50% 67.42% 8.89% Full course 42.10% 49.77% 0.00% Time to vaccination (months) 16 11.8 10.5 MMR Any dose 6.70% 10.86% 2.22% Time to vaccination (months) 33.4 30.4 <jats:td colsp