A phase I/II study of CpG/alum-adjuvanted mammalian-derived quadruple antigen carrying virus-like particle COVID-19 vaccine.

Background: Waning Spike-elicited immunity and emerging COVID-19 variants underscore the need for vaccines leveraging multiple SARS-CoV-2 antigens, rapidly adaptable to evolving strains. Herein, we evaluated the safety and immunogenicity of a CpG ODN-adjuvanted, alum-adsorbed, virus-like particle (VLP) vaccine displaying the hexaproline stabilized Spike (S) protein and the Nucleocapsid, Membrane, and Envelope proteins of SARS-CoV-2.

Methods: In phase 1 randomized, double-blind, placebo-controlled, dose-escalation trial, participants (N = 38, aged 18-59) received two subcutaneous injections of either 10 μg or 40 μg of VLP or placebo, 21 days apart.