LONG-TERM IMMUNITY TO MEASLES AFTER ALLOGENEIC HAEMATOPOIETIC CELL TRANSPLANTATION: FACTORS ASSOCIATED WITH SEROPROTECTION BEFORE REVACCINATION: Immunity to measles after HCT

Abstract Measles can be a life-threatening infection in immunocompromised patients, especially after allogeneic haematopoietic 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. Few data exist, however, on the rates of seroprotection to measles with the current conditioning regimens and in long-term follow-up. The objectives of the 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 transplanted 1–39 years ago (median: 9 years) were assessed for measles immunity. Measles immunoglobulin (Ig)G titers were determined with an automated chemiluminescent immunoassay. Seropositivity/seroprotection was defined by IgG titers > 16.5 UA/mL. Most patients were transplanted for acute leukaemia (61%) and after a reduced-intensity (RIC) or nonmyeloablative (NMA) regimen in 46% of them. Here, 78/126 (62%) of the patients were seropositive/seroprotected for measles. Among the seropositive patients, the patients who had been vaccinated before transplant had lower median IgG titers (48 UA/mL) than those who had not (116 UA/mL). Myeloproliferative disorder, RIC or NMA conditioning and absence of acute grade ≥ 2 graft-versus-host disease were associated with seropositivity/seroprotection. With a 62% rate of seropositivity/seroprotection for measles at a median of nine years after transplant, our findings strongly support a systematic assessment of antimeasles antibody titers to avoid unnecessary vaccination in seroprotected patients.