Durability and Cross-Reactivity of Immune Responses Induced by an AS03 Adjuvanted Plant-Based Recombinant Virus-Like Particle Vaccine for COVID-19

As the SARS-COV-2 pandemic evolves, what is expected of vaccines extends beyond efficacy and includes evaluations of both durability and cross-reactivity to emerging variants. To complement an on-going Phase 3 efficacy study, this report expands on previously reported immunogenicity results from a Phase 1 trial of an AS03-adjuvanted, plant-based virus-like particle (VLP) displaying the spike glycoprotein of the Wuhan strain of SARS-CoV-2 virus (NCT04450004). Durability of the humoral and cellular responses against the ancestral strain was evaluated 6 months post-second dose (Day 201) at which time [~]94% of vaccinated individuals remained seropositive. Interferon gamma (IFN-{gamma}) and interleukin 4 (IL-4) responses remained detectable in [~]94% and [~]92% of vaccinated individuals respectively. Cross-reactivity of neutralizing antibodies to Alpha (B.1.17), Beta (B.1.351), and Gamma (P.1) variants of concern (VOC) were also measured. Twenty-one days after the second vaccination, detectable neutralizing antibodies were observed to the Alpha variant by both pseudovirion and wild-type assays for all vaccinated individuals, while 94.7% of individuals had detectable antibodies to the Beta variant in both assays. Neutralizing antibodies to the Gamma variant were detected in 100% and 94.7% of individuals using the pseudovirion and live virus neutralization assays, respectively. In all cases, the vaccine-induced neutralizing GMTs to the VOC 3 weeks post-vaccination were greater than the Wuhan-specific neutralization titers seen in individuals recovered from COVID-19.