Immunization of Adult Hematopoietic Stem Cell Transplant Recipients: Current Recommendations and Clinical Practice

Following hematopoietic stem cell transplantation (HSCT), most previously acquired immunity is diminished or been lost, necessitating comprehensive revaccination, as recommended by both domestic and international guidelines. Immune reconstitution typically requires at least 1-2 years and is influenced by diverse factors such as age, transplant type, and graft-versus-host disease. Although vaccine immunogenicity is reduced during the early post-HSCT period due to profound immunosuppression, this is also when infection prevention is at its most critical. Consequently, the optimal timing of posttransplant vaccination remains a topic of debate among experts. Recently, several new vaccines have been approved in Japan, including recombinant zoster, higher-valent pneumococcal conjugate, and high-dose influenza vaccines. This review addresses the fundamental principles of post-HSCT vaccination and discusses specific considerations for representative vaccine-preventable diseases based on current evidence and vaccine availability.