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

StaphVAX(R), an unadjuvanted, bivalent vaccine composed of Staphylococcus aureus (S. aureus) capsular polysaccharides (CPS) types 5 and 8 bound to the mutant non-toxic recombinant Pseudonomas aeruginosa exotoxin A (rEPA) conferred similar to60% protection for 10 months against bacteremia caused by this pathogen in hemodialysis patients. A protective level of 80 mug/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 StaphVAX(R) in hemodialysis patients, recipients of the vaccine were reinjected in a randomized double-blinded, placebo-controlled study. Vaccinees received StaphVAX(R) and a saline placebo injection 14 days apart according to the randomization schedule. The booster dose of StaphVAX(R) 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 mug/ml at day 0 to 162 mug/ml (P < 0.001) and for type 8 front 59 mug/ml to 133 mug/ml (P < 0.001). Anti-CPS antibody levels of similar to80 mug/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. (C) 2004 Elsevier Ltd. All rights reserved.