Longitudinal Analysis of Antibody Response to Immunization in Pediatric Survivors After Allogeneic Hematopoietic Stem Cell Transplantation.

Abstract 795 Re-immunization is a common practice after allogeneic hematopoietic stem cell transplantation (allo-HSCT), but the optimal vaccine schedule and long-term response have not been established. We prospectively and longitudinally evaluated the antibody response to childhood vaccines in 210 survivors after allo-HSCT. Positive titer lasting for 5 years or more after immunization was observed more often for diphtheria (98.1%), tetanus (96.1%), rubella (92.9%), and polio vaccines (96.2% for type 1; 98.1% for type 2 and 3), but less often for pertussis (25.0%), measles (65.4%), mumps (64.3%), and hepatitis B (75.0%). As shown in the table below, vaccine failure was associated with patients who were older at the time of re-immunization, received a T cell depleted graft, had a high-risk hematological malignancy, lower IgG levels, higher IgM levels, chronic GvHD, positive recipient CMV status, and negative titers prior to immunization. These clinical factors are useful to formulate immunization and monitoring strategies for survivors after allo-HSCT. Patients at risk for vaccine failure should be monitored closely during long-term follow-up, and booster immunizations should be considered when there is no seroconversion.Table.Factors associated with negative titers after re-immunizationVaccineFactorOdds ratio95% confidence intervalp value DiphteriaT cell depleted graft5.521.14-26.820.034 TetanusOlder age at immunization1.541.05-2.220.026 Lower IgG level*1.031.00-1.050.033 MeaslesLower IgG level*1.011.00-1.020.022 MumpsHigh risk vs. standard risk2.631.02-6.670.045 RubellaHigher IgM level*1.121.03-1.230.012 High risk vs. standard risk16.71.56-100.000.02 PoliovirusType 1Older age at immunization1.431.05-1.920.021 Positive recipeint CMV titer3.181.58-6.410.001 Higher IgM level*1.081.01-1.150.027 Negative titer before immunization8.332.17-33.330.002 Type 2Older age at immunization1.411.04-1.920.027 Positive recipeint CMV titer2.651.36-5.200.004 Higher IgM level*1.061.00-1.140.04 Negative titer before immunization14.34.55-50.00<0.001 Type 3Older age at immunization1.411.04-1.890.027 Positive recipient CMV titer3.111.67-5.80<0.001 Higher IgM level*1.061.00-1.120.035 Chronic GVHD2.71.05-6.950.04 Negative titer before immunization5.881.92-20.000.002*Total IgG and IgM, not disease specific Ig levels Disclosures: No relevant conflicts of interest to declare.