Long-Term Immunity to Measles after Allogeneic Hematopoietic Cell Transplantation: Factors Associated with Seroprotection before Revaccination.

Measles can be a life-threatening infection in immunocompromised patients, especially after allogeneic hematopoietic cell transplantation (HCT) because of the corresponding loss of immunity. However, measles vaccines are live-attenuated, which is why measles vaccinations are recommended only in seronegative HCT recipients and in specific conditions. However, little data exist on the rates of seroprotection to measles with the current conditioning regimens and in long-term follow-up. The objectives of this study were to assess measles immunity before considering vaccination in a cohort of allogeneic HCT long-term survivors and to identify the factors associated with seropositivity/seroprotection. One hundred and twenty-six patients who underwent transplantation between 1 and 39 years earlier (median, 9 years) were assessed for measles immunity. Measles IgG titers were determined with an automated chemiluminescent immunoassay. Seropositivity/seroprotection was defined by an IgG titer >16.5 UA/mL. Patients underwent transplantation with a reduced-intensity conditioning (RIC) or nonmyeloablative (NMA) conditioning in 46% of cases, mainly for acute leukemia (61%). Seventy-eight of the 126 patients (62%) were seropositive/seroprotected for measles. Among the seropositive patients, the patients who had been vaccinated before transplantation had a lower median IgG titer compared with those who had not (48 UA/mL versus 116 UA/mL). Myeloproliferative disorder, RIC or NMA conditioning, and absence of acute grade ≥II graft-versus-host disease were associated with seropositivity/seroprotection. With a 62% rate of seropositivity/seroprotection for measles at a median of 9 years after transplantation, our findings strongly support a systematic assessment of anti-measles antibody titers to avoid unnecessary vaccination in seroprotected patients.