title: A phase 1, placebo-controlled, randomized study of the safety, tolerability, and immunogenicity of a Clostridium difficile vaccine administered with or without aluminum hydroxide in healthy adults.
abstract: BACKGROUND
  Clostridium difficile is a significant cause of morbidity and mortality in hospitals, nursing homes, and long-term care facilities. The bacteria can produce 3 toxins, of which the C. difficile toxin A and C. difficile toxin B are the principal virulence factors for C. difficile-associated disease.
  
  
  METHODS
  A phase 1, first-in-human, placebo-controlled, dose-escalation study was performed to assess the safety and immunogenicity of an investigational vaccine candidate consisting of genetically and chemically detoxified, purified toxins A and B. The toxoids, either alone or in combination with aluminum hydroxide (Al(OH)3), were administered to healthy adults 50-85 years of age at antigen dose levels of 50, 100, or 200 μg in a 3-dose regimen administered at 0, 1, and 6 months.
  
  
  RESULTS
  Overall, the C. difficile vaccine formulations and doses administered were generally well tolerated. Local reactions and systemic events were predominantly mild to moderate, were more common in the 50-64-year age cohort, and comprised mostly injection site pain, headache, and fatigue. In subjects who received the vaccine formulations, both the toxin A- and toxin B-specific neutralizing antibody geometric mean concentrations increased substantially at 1 month after Dose 2 and after Dose 3 compared to baseline. In the 50-64-year age cohort, geometric mean fold rises (GMFRs) in toxin A-specific neutralizing antibodies from baseline at Month 7 ranged from 59.19 to 149.23 in the vaccine groups compared to 2.47 in the control group. For toxin-B specific neutralizing antibodies, the GMFRs from baseline at Month 7 ranged from 116.67 to 2503.75 in the vaccine groups compared to 2.48 in the control group. In the 65-85-year age cohort, GMFRs in toxin A-specific neutralizing antibodies from baseline at Month 7 ranged from 42.73 to 254.77 in the vaccine groups compared to 2.03 in the control group. For toxin-B specific neutralizing antibodies, the GMFRs from baseline at Month 7 ranged from 136.12 to 4922.80 in the vaccine groups compared to 1.58 in the control group. Potent antitoxin neutralizing responses were still evident in immunized subjects in both age groups at Month 12. Although there was no clear dose-level response pattern, the data suggest that both the antitoxin A- and B-specific neutralizing responses were trending higher in the toxoid-only groups compared to the toxoid+Al(OH)3 groups. Furthermore, the magnitude of the immune response was similar in the 2 age cohorts.
  
  
  CONCLUSIONS
  The vaccine formulations studied in this phase 1 study were immunogenic and well tolerated. The results presented support further development of the C. difficile vaccine candidate in a larger population of subjects to determine the optimal dose and immunization schedule.
  
  
  BACKGROUND
  NCT01706367.
authors.affiliation: Miami Research Associates, 6141 Sunset Drive, Suite 501, South Miami, FL 33143, United States.
authors.forename: Eric
authors.initials: E
authors.lastname: Sheldon
authors.affiliation: Pfizer Vaccine Research & Development, Walton Oaks, Dorking Road, Tadworth, Surrey KT20 7NS, United Kingdom. Electronic address: nicholas.kitchin@pfizer.com.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Kitchin
authors.affiliation: Pfizer Vaccine Research & Development, 401 North Middletown Road, Pearl River, NY 10965, United States.
authors.forename: Yahong
authors.initials: Y
authors.lastname: Peng
authors.affiliation: Pfizer Vaccine Research & Development, 401 North Middletown Road, Pearl River, NY 10965, United States.
authors.forename: Joseph
authors.initials: J
authors.lastname: Eiden
authors.affiliation: Pfizer Vaccine Research & Development, 401 North Middletown Road, Pearl River, NY 10965, United States.
authors.forename: William
authors.initials: W
authors.lastname: Gruber
authors.affiliation: Pfizer Vaccine Research & Development, 401 North Middletown Road, Pearl River, NY 10965, United States.
authors.forename: Erik
authors.initials: E
authors.lastname: Johnson
authors.affiliation: Pfizer Vaccine Research & Development, 401 North Middletown Road, Pearl River, NY 10965, United States.
authors.forename: Kathrin U
authors.initials: KU
authors.lastname: Jansen
authors.affiliation: Pfizer Vaccine Research & Development, 401 North Middletown Road, Pearl River, NY 10965, United States.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Pride
authors.affiliation: Pfizer Vaccine Research & Development, 401 North Middletown Road, Pearl River, NY 10965, United States.
authors.forename: Louise
authors.initials: L
authors.lastname: Pedneault
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage*; D000368:Aged; D000369:Aged, 80 and over; D000536:Aluminum Hydroxide / Q000008:administration & dosage*; D000907:Antibodies, Bacterial / Q000097:blood; D057134:Antibodies, Neutralizing / Q000097:blood; D001428:Bacterial Vaccines / Q000008:administration & dosage / Q000627:therapeutic use*; D016360:Clostridioides difficile; D004761:Enterocolitis, Pseudomembranous / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007117:Immunization, Secondary; D008297:Male; D008875:Middle Aged; D016037:Single-Blind Method; D014121:Toxoids / Q000008:administration & dosage / Q000627:therapeutic use
chemical_list: D000276:Adjuvants, Immunologic; D000907:Antibodies, Bacterial; D057134:Antibodies, Neutralizing; D001428:Bacterial Vaccines; D014121:Toxoids; D000536:Aluminum Hydroxide
keywords: Clostridium difficile; Neutralizing antibody; Pseudomembranous colitis; Toxin A; Toxin B; Vaccine