Safety, immunogenicity and dose response of VLA84, a new vaccine candidate against Clostridium difficile, in healthy volunteers.

Abstract Background Clostridium difficile infection (CDI) is the leading cause of antibiotic-associated diarrhoea and colitis and the most common pathogen of health care-associated infections. In the US, CDI causes approximately half a million infections and close to 30,000 deaths. Despite antibiotic treatment of C. difficile associated diarrhoea, the disease is complicated by its recurrence in up to 30% of patients. Methods An open-label, partially randomized, dose-escalation Phase I trial was performed in two parts. Sixty volunteers aged ≥18 to Results VLA84 was safe and well tolerated. Fifty-one adult volunteers (85%) and 50 elderly (62%) experienced at least one solicited or unsolicited adverse event (AE). Forty-eight adult volunteers (80%) and 40 elderly (49%) experienced related AEs which were mostly mild or moderate. No related serious adverse event and no death occurred. The vaccine induced high antibody titres against Toxin A and Toxin B in both study populations. Conclusion VLA84 was safe, well tolerated and highly immunogenic in adult volunteers aged ≥18 to This study is registered at ClinicalTrials.gov under registration number NCT01296386 .