S-268019-b

S-268019-b is a recombinant protein subunit vaccine developed by Shionogi for the prevention of COVID-19. It consists of a full-length recombinant SARS-CoV-2 spike (S) protein antigen (S-910823), produced in insect cells using the baculovirus expression system, and formulated with a squalene-based oil-in-water emulsion adjuvant (A-910823). The vaccine is administered intramuscularly. Clinical trials have demonstrated that S-268019-b induces robust neutralizing antibody responses and T-helper 1-mediated cellular immunity, with reactogenicity generally mild and no serious treatment-related adverse events reported. It has been evaluated as both primary vaccination and as a booster dose, showing non-inferiority to mRNA vaccines such as BNT162b2 in boosting neutralizing antibodies against SARS-CoV-2, including variants like Omicron.