Antibody responses in Hematopoietic cell transplantation recipients after vaccination against Haemophilus Influenzae type B and streptococcus pneumoniae

Purpose: Hematopoietic cell transplantation (HCT) recipients are vulnerable to invasive infection by Haemophilus influenzae type b (Hib) and Streptococcus pneumoniae (Sp). This study was performed to evaluate immune responses after Hib and Sp vaccination in Korean pediatric HCT recipients. Methods: Patients were prospectively enrolled at Samsung Medical Center during 2009-2011. ELISA tests to detect anti-PRP IgG antibody and antibodies to Sp serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F were performed at the Center for Vaccine Evaluation and Study, Ewha Medical Research Institute. Results: Ten patients (two allogeneic, eight autologous recipients) with median age 5.4 years (range 2.7-12.2 years) were enrolled. Before Hib vaccination, 60% of patients' anti-PRP IgG titers were below 0.15 μg/mL. After vaccination, 100% of patients' anti-PRP IgG titers increased above 0.15 μg/mL (cut-off value for detection) and 1.0 μg/mL (cut-off value for seroprotection). For pneumococcus, in 2-5 year-old patients, pre-vaccination geometric mean concentrations (GMCs) of IgG for six serotypes (4, 6B, 9V, 14, 18C, and 23F) were below 0.35 μg/mL and at 5 months post-vaccination GMCs of IgG for all seven serotypes increased to above 0.35 μg/mL. In patients older than 5 years, pre-vaccination GMCs of IgG for four serotypes (4, 9V, 14, and 23F) were below 0.35 μg/mL and at 3 months post-vaccination GMCs of IgG for all seven serotypes increased to above 0.35 μg/mL. Conclusion: Most HCT recipients had low or no protective antibodies to Hib and Sp before vaccination, but showed good immune responses to protective levels after vaccination.