"Catch-Up Vaccinations Post-Stem Cell Transplant: A case series and review of the literature"

Stem cell transplantation (SCT), including autologous and allogeneic approaches, is a potentially curative therapy for various hematologic malignancies and selected non-malignant disorders. Autologous stem cell transplantation (ASCT) is an established curative treatment for hematologic malignancies, including Hodgkin lymphoma (HL). Non-Hodgkin Lymphoma (NHL), and Multiple Myeloma (MM), but infectious complications remain a major challenge. Vaccination is an essential strategy to reduce the risk of vaccine-preventable infections following transplant. This case series describes immunocompromised patients with relapsed or refractory hematologic malignancies who underwent ASCT and were referred for post-transplant immunization. We present a catch-up and COVID-19 vaccination schedule using minimum recommended intervals, with emphasis on immunocompromised hosts and post-ASCT maintenance therapies. Post-ASCT maintenance therapies such as rituximab may impair humoral responses and reduce vaccine immunogenicity; however, current guidelines support prioritized use of inactivated vaccines, including pneumococcal conjugate vaccines (PCV-13) followed by Pneumococcal Polysaccharide vaccine (PPSV-23) and annual inactivated influenza vaccination. Vaccination timing should consider B-cell-depleting therapies to optimize immune response, while live attenuated vaccines remain contraindicated during ongoing immunosuppression. Vaccines were well tolerated, with only mild injection-site reactions reported.