760. Safety and Immunogenicity of a Novel Clostridium difficile Candidate Vaccine in Adults and the Elderly
Session: Oral Abstract Session: Clostridium difficile: Detection, Transmission, and Treatment
Friday, October 21, 2011: 4:00 PM
Room: 151AB
Background: The safety, tolerability, immunogenicity and kinetics for a range of doses of a candidate Clostridium difficile toxoid vaccine were studied in adults (18-55 years) and the elderly (≥65 years).

Methods: Two Phase I, multi-center, randomized, double-blind, placebo-controlled trials in adult and elderly subjects. The investigational vaccine (N=36 [each group]) or placebo (N=12 [each group]) was injected intramuscularly on Days 0, 28 and 56. IgG specific for C. difficile toxins A and B were assessed on these days and on Days 70 and 236. Blood chemistry, hematology and urinalysis were assessed at defined timepoints and safety was assessed between visits using diary cards. Subjects were followed for 6 months after the third injection. Analyses were descriptive.

Results: Seroconversion rate (%) (≥4-fold increase from baseline for specific IgG levels):

 

18-55 years

 

≥65 years

 

2 µg

(N=13)

10 µg

(N=12)

50 µg

(N=11)

Total

(N=36)

 

2 µg

(N=12)

10 µg

(N=9)

50 µg

(N=11)

Total

(N=32)

Anti-toxin A

 

 

 

 

 

 

 

 

 

   Day: 14

NC

NC

NC

NC

 

0

11

27

13

            28

46

42

91

58

 

17

22

36

25

            56

100

100

100

100

 

50

89

100

78

            70

100

100

100

100

 

92

100

100

97

Anti-toxin B

 

 

 

 

 

 

 

 

 

   Day: 14

NC

NC

NC

NC

 

17

22

36

25

            28

15

42

64

39

 

25

22

45

31

            56

23

50

64

44

 

33

44

45

41

            70

46

58

73

58

 

58

56

73

63

NC=not calculated

There was no seroconversion in the placebo group. For toxin A, 100% of subjects aged 18-55 years had seroconverted by Day 56, as had all those >65 years receiving the 50 µg dose. Anti-toxin B seroconversion was lower than for anti-toxin A and was highest for the 50 µg dose in each age group and at each timepoint. At Day 236, mean titers for both anti-toxin A and B were greater than baseline in each age and dose group. There were no safety concerns, and no vaccine-related SAEs.

Conclusion: The candidate vaccine was immunogenic for toxin A and B in both age groups and was well tolerated.


Subject Category: I. Adult and Pediatric Vaccines

Richard N Greenberg, MD, Univ. of Kentucky Medical Center, Lexington, KY, Thomas Marbury, MD, Orlando Clinical Research Center, Orlando, FL and Ginamarie Foglia, DO, MPH, Clinical Development, Sanofi Pasteur, Swiftwater, PA

Disclosures:

R. N. Greenberg, Sanofi Pasteur, Pfizer, PaxVax, Virxsys, Bavarian Nordic: Investigator, Clinical trial costs

T. Marbury, None

G. Foglia, Sanofi Pasteur: Employee and Shareholder, Salary

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