Long-term immunity to measles and rubella after vaccination in adult allogeneic hematopoietic stem cell transplant recipients.

Outbreaks of measles and rubella occasionally occur, and allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients face an increased risk of mortality from measles. This retrospective observational study assessed immunological responses to MR vaccination and long-term changes in antibody titers in adult allo-HSCT recipients. The measles and rubella cohorts included 36 and 33 patients, respectively, who received MR vaccination between March 2010 and December 2023. MR vaccination significantly increased IgG titers against measles from 5.48 (± 3.61) at T0 (pre-vaccination) to 14.15 (± 10.31) at T1 (1 year post-vaccination) and against rubella from 3.90 (± 2.82) at T0 to 58.93 (± 44.46) at T1 (both p < 0.001). Multivariate analyses in the measles cohort showed that lower IgG antibody titers at T0 were significantly associated with high responder status (OR 0.57, 95% CI 0.35-0.96, p = 0.029). High responders had significant mean changes in IgG antibody titers from T0 to each time point from T1 to T5 (5 years post-vaccination) for both measles and rubella. The annual decline in IgG titers was predicted to be 2.14 (p = 0.002) for measles and 3.15 (p = 0.51) for rubella in high responders. Despite high antibody titers, these levels decline over time, emphasizing the importance of regular monitoring and potential revaccination.