121. Safety, Tolerability, and Pertussis Immunogenicity Findings From a Randomized, Participant-Blinded, Active-Controlled, Dose-Escalating, Phase 1 Trial of a Tetanus/Diphtheria/Pertussis Booster Vaccine (Tdap-1018 CpG Adjuvanted) Compared With Boostrix in Healthy Adults Aged 18 to 22 Years

Abstract Background Bordetella pertussis is a gram-negative bacterium causing the highly contagious respiratory infection pertussis in over 151 000 individuals annually worldwide. A tetanus/diphtheria/pertussis (Tdap) vaccine combined with CpG 1018 adjuvant (Tdap-1018) may induce higher antibody titers than existing aluminum-adjuvanted Tdap vaccines used as a booster in adults. Methods In this randomized, active-controlled, participant-blinded, phase 1 trial, healthy adults aged 18 to 22 years received 1 booster injection of Tdap-1018 (with same Tdap composition as in Boostrix and escalating CpG 1018 dose of 1500 µg and 3000 µg) or Boostrix on Day 1. Pertussis immunogenicity evaluations assessed booster response rates (BRRs) for anti-pertussis toxin (anti-PT), anti-filamentous hemagglutinin (anti-FHA), and anti-pertactin (anti-PRN) antibodies, and systems serology at Week 4 post-vaccination. Safety and tolerability were assessed for solicited local and systemic post-injection reactions for 7 days and unsolicited adverse events for 12 weeks after vaccination. Results Of the 87 enrolled adult participants, 84 had post-vaccination immunogenicity results. The median age was 19.0 years, 35% were men, and 83% were white. At Week 4, BRRs in the Tdap-1018 3000 µg group were statistically significantly higher (based on lower 95% confidence interval [CI] >0%) than the Boostrix group for anti-PT (difference in BRRs 22.2% [95% CI: 1.5%–42.8%]) and anti-PRN (22.2% [95% CI: 8.2%–40.9%]) antibodies, and similar for anti-FHA (14.8% [95% CI: -2.6%–33.9%]) antibodies (Table). Tdap-1018 1500 µg, Tdap-1018 3000 µg, and Boostrix were generally well tolerated with no observed safety concerns. Conclusion In this phase 1 trial, both dose levels of Tdap-1018 were generally well tolerated. Tdap-1018 3000 µg induced statistically significantly higher BRRs than Boostrix for anti-PT and anti-PRN, and a similar response for anti-FHA antibodies. Disclosures Robert Janssen, MD, Dynavax Technologies Corporation: employee|Dynavax Technologies Corporation: Stocks/Bonds Tammy Boyce, MEd, Dynavax Technologies Corporation: Employee|Dynavax Technologies Corporation: Stocks/Bonds Fang Xie, PhD, Dynavax Technologies Corporation: Employee|Dynavax Technologies Corporation: Stocks/Bonds Olivier Godeaux, MD, MPH, Dynavax: Advisor/Consultant.