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

Vaccine. 2016 May 17;34(23):2585-92. doi: 10.1016/j.vaccine.2016.03.098. Epub 2016 Apr 11.


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 <65 years were randomized into five treatment groups to receive three immunizations (Day 0, 7, 21) of VLA84 (20μg with Alum, 75μg with or without Alum, 200μg with or without Alum). Eighty-one volunteers aged ≥65 were randomized into four treatment groups (75μg with or without Alum, 200μg with or without Alum) and received four immunizations (Day 0, 7, 28 and 56). All subjects were followed for safety and immunogenicity for six months.

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 <65 years and elderly volunteers aged ≥65 years. This study is registered at under registration number NCT01296386.

Keywords: C. difficile; C. difficile associated diarrhoea (CDAD); C. difficile infection (CDI); C. difficile vaccine.

Publication types

  • Clinical Trial, Phase I
  • Randomized Controlled Trial

MeSH terms

  • Adjuvants, Immunologic / administration & dosage
  • Adult
  • Aged
  • Alum Compounds / administration & dosage
  • Anti-Bacterial Agents / adverse effects
  • Antibodies, Bacterial / blood
  • Bacterial Proteins / immunology*
  • Bacterial Toxins / immunology*
  • Bacterial Vaccines / therapeutic use*
  • Clostridioides difficile
  • Clostridium Infections / prevention & control*
  • Diarrhea / chemically induced
  • Dose-Response Relationship, Immunologic
  • Enterotoxins / immunology*
  • Female
  • Humans
  • Immunization, Secondary
  • Male
  • Middle Aged
  • Neutralization Tests
  • Recombinant Proteins / immunology
  • Young Adult


  • Adjuvants, Immunologic
  • Alum Compounds
  • Anti-Bacterial Agents
  • Antibodies, Bacterial
  • Bacterial Proteins
  • Bacterial Toxins
  • Bacterial Vaccines
  • Enterotoxins
  • Recombinant Proteins
  • tcdA protein, Clostridium difficile
  • toxB protein, Clostridium difficile
  • aluminum sulfate

Associated data