LB13. Trivalent Hepatitis B (HepB) Vaccine Yields Superior Seroprotection Rates in Adults: Results from the Phase 3 Double-Blind, Randomized Study Comparing Immunogenicity and Safety of a 3-Dose Regimen of Sci-B-Vac™ and Engerix B® (PROTECT)

BACKGROUND: Many adults fail to achieve seroprotection after receiving 3 doses of monovalent HepB vaccines such as Engerix-B® and the response decreases with age and with common co-morbidities. Sci-B-Vac™ is a trivalent HepB vaccine produced in mammalian cells, adjuvanted with aluminum hydroxide, which in addition to small S antigen, contains preS1 and preS2 antigens expressing highly immunogenic T- and B-cell epitopes that may enhance seroprotection rates (SPR) in adults. METHODS: In a multicentre study, the immunogenicity of 10 µg dose of Sci-B-Vac™ was compared with a 20-µg dose of Engerix-B® given at days 0, 28, and 168 (NCT03393754). Randomization was stratified by study center and age (18–44, 45–64, ≥65 years). Immunogenicity, including SPR (% subjects with anti-HBs levels ≥10 mIU/mL), and safety outcomes were followed to Day 336. The co-primary objectives were (1) non-inferiority in adults ≥18 years and (2) superiority in adults ≥45 years of SPR, 4 weeks after the third dose. RESULTS: Of 1,607 randomized subjects, 42.3% were from United States, 41.6% EU, and 16.1% Canada. Males (38.5%) and females (61.5%) were enrolled to 18–44 (18.6%), 45–64 (44.6%), and ≥ 65 year (36.8%) age groups. Both co-primary endpoints were met. In the non-inferiority analysis, SPR in Sci-B-Vac™ recipients aged ≥18 years was 91.4% vs. 76.5% for Engerix-B®; SPR difference: 14.9%; 95% confidence interval (CI) [11.2%, 18.6%]. Superiority analysis showed that SPR in Sci-B-Vac™ recipients aged ≥45 years was 89.4% vs. 73.1% for Engerix-B®—SPR difference: 16.4%; 95% CI [12.2%, 20.7%] (figure). Significantly higher SPR for Sci-B-Vac™ vs. Engerix-B® was noted in subgroups (gender, BMI, diabetes, smoking and particularly age—SPR difference for 45–64 (14.7% [9.8–19.8%]) and ≥ 65 (18.9% [11.6–26.1%]) years. No major safety signals were observed; solicited and unsolicited adverse events were consistent with the known vaccine safety profiles. CONCLUSION: Sci-B-Vac™ met immunogenicity endpoints for non-inferiority in adults aged ≥ 8 years and was superior in adults aged ≥45 years, compared with the monovalent vaccine, Engerix-B®. Sci-B-Vac™ SPR was higher compared with Engerix-B® in key subgroups. No safety signals were observed and safety and tolerability were consistent with the known profile of Sci-B-Vac™. [Image: see text] DISCLOSURES: Timo Vesikari, MD, VBI (Grant/Research Support, I have received funding from VBI to carry out the reported clinical trial in Finland), Joanne M. Langley, MD, VBI Vaccines (Grant/Research Support), Johanna Spaans, BSc, MSc, VBI Vaccines (Employee), Nathalie Machluf, PhD, SciVac Ltd. (Employee), Dave Anderson, PhD, VBI Vaccines, Inc. (Employee, Shareholder), Vlad Popovic, MD, VBI Vaccines (Employee), Francisco Diaz-Mitoma, MD, VBI Vaccines, Inc. (Consultant, Shareholder, Independent Contractor). Other Authors: No reported disclosures.