Phase I dose finding studies of an adjuvanted Clostridium difficile toxoid vaccine
Fifty healthy adult (18–55 years) and 48 elderly (≥65 years) volunteers were randomized to receive a candidate Clostridium difficile toxoid vaccine (2 Î¼g, 10 Î¼g, or 50 Î¼g) or placebo on Days 0, 28, and 56. No volunteer receiving placebo seroconverted. For toxin A, seroconversion by Day 56 (post-dose 2) was observed in 100% of volunteers aged 18–55 years in all dose groups and in 50%, 89%, and 100% of elderly participants in the 2 Î¼g, 10 Î¼g, and 50 Î¼g dose groups, respectively. For both age groups, seroconversion for toxin B was lower than toxin A. There were no safety concerns.