Serologic Investigation of Pneumococcal Immunization of Autologous Hematopoietic Stem Cell Recipients

Our goal was to prospectively assess the immunological response to the 23-valent pneumococcal polysaccharide vaccine (PPSV23) in autologous cell transplantation (AHCT) recipients using pneumococcal IgG (PNEIGG) titers. PNEIGG titers were collected prior to transplant (titer 1), 3-7 days following AHCT (titer 2), 1 year later at the time of vaccination (titer 3), and at 4-6 wks after vaccination (titer 4) for each of the 23 serotypes included in PPSV23. Seroreactivity was defined as a =4-fold increase in titer or a titer of >1.3 µg/mL following vaccination. Only 2 of 10 AHCT recipients with data through titer 4 were seroreactive in the majority of the 23 pneumococcal serotypes following PPSV23 which were not prior to vaccination. Median titer concentration increase reached the threshold for seroreactivity only for serotypes 12F and 15B. Antibody response of the 5 serotypes analyzed (4,8,12F,14,19F) was significantly lower in the AHCT population compared to healthy historical controls. There appears to be minimal immunogenicity as measured by PNEIGG titers to PPSV23 one year following AHCT.