Shingrix In Recipients of Allogeneic Transplants

This study investigates whether a third (booster) dose of the Shingrix vaccine — the recombinant zoster vaccine (RZV) used to prevent shingles (herpes zoster) — is safe and effective for people who have previously received the standard two-dose Shingrix series after an allogeneic stem cell transplant (allo-SCT). Recipients of stem cell transplants have severely weakened immune systems and face a much higher risk of shingles than the general population. The standard two-dose primary series is given starting one year after transplant, but immunity may wane over time — this study asks whether a third dose can restore or boost protection. Adults aged 18–79 who received an allo-SCT, then completed their two-dose primary RZV series at least 1 year after the transplant, and have been enrolled at least 18 months after that second dose, are eligible. Participants must not have active Graft Versus Host Disease, must not be on high-dose immunosuppression beyond graft maintenance, must not have recently received live vaccines, and must not be pregnant or breastfeeding. Participants receive the third vaccine dose and are followed for immune response and safety. Shingles in immunocompromised patients is far more severe than in healthy adults — causing intense pain, nerve damage, and serious complications. A well-timed booster strategy to maintain protection in this population could prevent significant suffering.