Antibody responses in postsplenectomy trauma patients receiving the 23-valent pneumococcal polysaccharide vaccine at 14 versus 28 days postoperatively.

Background: We 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 (microg/mL) and OPA titer (1/dilution) after vaccination. There were no statistically significant differences (p >or= 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.