A randomized, double-blind, placebo-controlled trial to evaluate the prime-boost strategy for pneumococcal vaccination in adult liver transplant recipients.

Background: The 23-valent pneumococcal polysaccharide vaccine (PPV23) is recommended for disease prevention in solid-organ transplant recipients, but it may have suboptimal immunogenicity. It may be possible to enhance immunogenicity by priming the recipient with the 7-valent pneumococcal conjugate vaccine (PCV7), followed by boosting with PPV23.

Methods: We randomized adult liver transplant recipients to receive either (1) PCV7 followed by a PPV23 booster 8 weeks later (the "primed" group) or (2) placebo followed by a standard single dose of PPV23 (the "unprimed" group). Quantitative and functional antibody titers for 7 serotypes contained in both vaccines were measured at baseline, 8 weeks after enrollment, and 16 weeks after enrollment. Of 130 randomized patients, 113 completed the study.

Results: At week 16, response to at least 1 serotype was seen in 48 (85.7%) of 56 and 52 (91.2%) of 57 patients for the primed and unprimed groups, respectively (P=not significant). The mean number of serotypes to have responded (+/-SD) was 307+/-2.3 and 4.4+/-2.2 for the primed and unprimed groups, respectively (P=not significant). Functional antibody titers, which were measured with use of the opsonophagocytic assay, were also similar in both groups.

Conclusions: The immunogenicity of pneumococcal vaccination was not enhanced by the prime-boost strategy, compared with vaccination with PPV23 alone. Administration of a single dose of PPV23 should continue to be the standard of care for adult liver transplant recipients.

Clinical Trials Registration: NCT00152802 (http://www.clinicaltrials.gov).