Safety and immunogenicity of a booster dose of Staphylococcus aureus types 5 and 8 capsular polysaccharide conjugate vaccine (StaphVAXReg.) in hemodialysis patients.

摘要

StaphVAXReg., an unadjuvanted, bivalent vaccine composed of Staphylococcus aureus (S. aureus) capsular polysaccharides (CPS) types 5 and 8 bound to the mutant non-toxic recombinant Pseudomonas aeruginosa exotoxin A (rEPA) conferred ~60% protection for 10 months against bacteremia caused by this pathogen in hemodialysis patients. A protective level of 80 micro g/ml was estimated based upon geometric mean (GM) antibody levels at the end of the efficacy period. To extend the duration of protection conferred by StaphVAXReg. in hemodialysis patients, recipients of the vaccine were reinjected in a randomized double-blinded, placebo-controlled study. Vaccinees received StaphVAXReg. and a saline placebo injection 14 days apart according to the randomization schedule. The booster dose of StaphVAXReg. was administered an average of 958 days (753-1167 days) after the first injection. There were no serious adverse reactions. Antibody levels at day 14, 28, 92, and 182 post-injection were measured by ELISA. Maximal levels of IgG anti-CPS were observed at the 28-day interval. For type 5, GM antibody levels increased from 73 micro g/ml at day 0 to 162 micro g/ml (P<0.001) and for type 8 from 59 micro g/ml to 133 micro g/ml (P<0.001). Anti-CPS antibody levels of ~80 micro g/ml to type 5 and type 8 were achieved in 72.4 and 74.3% of vaccinees, respectively. There was excellent correlation between the level of anti-CPS and opsonic titer (r=0.93). Moreover, the decline of anti-CPS antibody levels at six months was significantly less rapid than that observed from the first immunization (P<0.001). We conclude that a booster immunization to maintain protective levels of specific antibodies for an extended period of time is feasible for patients at continuous risk for S. aureus bacteremia.