Comparison of two immunization schedules for a Pseudomonas aeruginosa outer membrane proteins vaccine in burn patients

The aim of the present study was to compare two immunization schedules for a Pseudomonas aeruginosa outer membrane proteins (OMPs) vaccine in burn patients. In a double-blind, randomized and placebo-controlled clinical trial, 95 adult patients with burn injuries in 10% or greater of total body surface area were randomly allocated to either placebo or immunization groups. Three doses of the vaccine (0.5 or 1.0 mg) were administered intramuscularly at either 3- or 7-day intervals. The vaccine was well tolerated, and no severe adverse reactions were observed in any of the vaccinees. After three immunizations, 88 patients were available for evaluation of serum antibody titers. Elevation of OMPs-specific antibody titers in the immunization groups was significantly higher as compared with the placebo group, and the highest antibody response was obtained by immunization with 1.0-mg doses at 3-day intervals. Conventional blood culture, tissue culture of wound biopsy specimens and a nested polymerase chain reaction (PCR) assay of blood specimens were performed to determine the protective efficacy. The results of the nested PCR indicated that the overall detection rate of P. aeruginosa in blood was significantly lower among immunized patients than placebo patients (6.1 vs. 40.0%, P < 0.001). Based on these results, we concluded that the P. aeruginosa OMPs vaccine is safe and highly immunogenic in burn patients, especially with 1.0-mg doses at 3-day intervals, and may be effective in conferring protection against P. aeruginosa bacteremia in burn patients. (C) 2000 Elsevier Science Ltd. All rights reserved.