Antibody Responses in Postsplenectomy Trauma Patients Receiving the 23-Valent Pneumococcal Polysaccharide Vaccine at 14 versus 28 Days Postoperatively

BACKGROUNDWe have previously demonstrated, using functional antibody assays, that patients undergoing splenectomy for trauma exhibit a better response to pneumococcal immunization when vaccinated at 14 days postoperatively versus 1 or 7 days. However, patients immunized at 14 days failed to reach the response of normal controls. This study was conducted to determine whether even later immunization would improve the antibody response. METHODS Forty surviving patients undergoing emergent splenectomy were randomized to receive Pneumovax at 14 or 28 days after splenectomy. Blood samples were drawn at the time of vaccination (prevaccination) and 4 weeks later (postvaccination). A control group of 24 healthy adults was used for comparison. Antibody titers to four of the most common serotypes were determined by enzyme-linked immunosorbent assay and opsonophagocytic assay (OPA). RESULTS Samples from 38 patient were analyzed. Each serotype and each group tested demonstrated a statistically significant increase in geometric mean enzyme-linked immunosorbent assay immunoglobulin G antibody concentration (μg/mL) and OPA titer (1/dilution) after vaccination. There were no statistically significant differences (p ≥ 0.07) in the immunoglobulin G antibody concentrations and OPA titers between the 14-day or the 28-day study groups when compared with normal healthy adults regardless of the serotype tested. In addition, there were no differences in the antibody responses between the 14-day and the 28-day study groups. CONCLUSION Despite our previous study suggesting that delay in vaccination after emergent splenectomy resulted in improved antibody response, antibody response was not improved any further by delaying vaccination to 28 days.