1. A Phase 2 Extension Study Evaluating the Immunogenicity, Safety, and Tolerability of 3 or 4 Doses of a Clostridioides difficile Vaccine in Healthy US Adults Aged 65 to 85 Years.
- Author
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Remich, Shon, Kitchin, Nicholas, Peterson, James, Li, Ping, Pride, Michael W, Brock, Linda, Anderson, Annaliesa S, Gruber, William C, Jansen, Kathrin U, Lockhart, Stephen P, and Webber, Chris
- Subjects
CLOSTRIDIOIDES difficile ,IMMUNE response ,CLINICAL trial registries ,VACCINE effectiveness ,VACCINE safety - Abstract
Background This phase 2 extension explored the long-term antibody persistence of an investigational Clostridioides difficile vaccine and the safety, tolerability, and immunogenicity of dose 4 approximately 12 months post–dose 3. Methods One year post–dose 3, healthy US 65- to 85-year-olds (N = 300) were randomized to dose 4 of vaccine at previously received antigen levels (100 or 200 μg) or placebo. Assessments included safety and percentages of participants achieving neutralizing antibody titers above prespecified thresholds (≥219 and ≥2586 neutralization units/mL for toxins A and B, respectively). Results In participants previously given three 200-µg doses and placebo in the extension, toxin A and B neutralizing antibodies were above prevaccination levels 48 months post–dose 3 (36 months after placebo); 24.0% and 26.0% had toxin A and B antibodies at or above prespecified thresholds, respectively. Neutralizing antibodies increased post–dose 4 (12 months post–dose 3) and persisted to 36 months post–dose 4. Thirty days post–dose 4, all participants had toxin A and 86.5% to 100% had toxin B titers at or above prespecified thresholds. Local reactions were more frequent in vaccine recipients. Systemic and adverse event frequencies were similar across groups. Conclusions C difficile vaccine immune responses persisted 48 months post–dose 3. Dose 4 was immunogenic and well tolerated, supporting continued development. Clinical Trials Registration. ClinicalTrials.gov NCT02561195. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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