Immunogenicity of pneumococcal vaccine in renal transplant recipients--three year follow-up of a randomized trial.

Routine pneumococcal vaccination is recommended at regular intervals posttransplant. However, there is limited data on durability of vaccine response and the impact of vaccine type on antibody persistence. We determined the durability of response for patients enrolled in a randomized trial of conjugate (PCV7) versus polysaccharide (PPV23) pneumococcal vaccination. Response was defined as a twofold increase from baseline and a titer ≥0.35 μg/mL using a pneumococcal ELISA for seven serotypes (measured at 8 weeks and 3 years). Forty-seven patients were evaluated and had received either PPV23 (n = 24) or PCV7 (n = 23). Response rates and geometric mean titers varied by serotype but declined significantly at 3-years for 6 of 7 serotypes (p < 0.001). No significant difference in durability was found in patients that had received PPV23 versus PCV7. Compared to the 8-week response, 20.6% fewer patients had a response to at least one serotype by 3 years. The largest relative declines were seen for serotype 4 (response dropped from 40.4% at 8 weeks to 17.0% at 3 years) and serotype 9V (44.7% dropping to 21.3%). The only factor predictive of response durability was a strong multiserotype initial response (p < 0.001). In conclusion, vaccine responses decline significantly by 3 years and conjugate vaccine does not improve the durability of response.