Immunogenicity and safety of an investigational hepatitis B vaccine with a Toll-like receptor 9 agonist adjuvant (HBsAg-1018) compared to a licensed hepatitis B vaccine in healthy adults 40–70 years of age☆

Abstract Background The currently licensed hepatitis B vaccines have limitations including hyporesponsiveness in older adults, poor compliance, and the extended time for most persons to develop seroprotection (e.g. >6 months). A vaccine containing HBsAg combined with a Toll-like receptor 9 agonist adjuvant (HBsAg-1018) has been developed to overcome these limitations. Methods A Phase 3, multicenter, randomized, subject- and observer-blinded, active-controlled trial was conducted among healthy subjects 40–70 years of age comparing the immunogenicity and safety of two doses of HBsAg-1018 at 0 and 4 weeks to three doses of licensed hepatitis B vaccine, HBsAg-Eng, at 0, 4, and 24 weeks. The primary immunogenicity endpoint was noninferiority of the seroprotection rate (SPR; % with anti-HBs ≥10 mIU/mL) of HBsAg-1018 compared to the SPR of HBsAg-Eng at 8 weeks following the last dose of vaccine. Conditional upon meeting noninferiority, superiority of HBsAg-1018 over HBsAg-Eng was assessed. Safety was compared between the two vaccines. Results At the primary endpoint, the SPR for the HBsAg-1018 group (90.0%) was superior to the SPR for the HBsAg-Eng group (70.5%) with an SPR difference of 19.5% (95% CI, 14.7%, 24.7%). At week 28 when the SPR peaked in the HBsAg-Eng group (72.8%), the SPR in the HBsAg-1018 group (94.8%) was significantly higher than in the HBsAg-Eng group. The SPR in the HBsAg-1018 group was significantly higher than in the HBsAg-Eng group at each study visit from week 4 through week 52. The safety profiles for the two vaccines were similar. Conclusion When compared to the HBsAg-Eng three-dose regimen given at 0, 1, and 6 months, HBsAg-1018 demonstrated superior seroprotection with only two doses at 0 and 1 month. The safety profile of HBsAg-1018 was comparable to that of the licensed vaccine, HBsAg-Eng. HBsAg-1018 would provide a significant public health contribution toward the prevention of hepatitis B infection.