Bivalent (Omicron BA.5/ancestral) recombinant spike protein vaccine: a promising booster

With the emergence of Omicron variants, which carry several immune escape-related mutations in the spike protein, the effectiveness of COVID-19 prototype vaccines was weakened.1,2 To overcome such weakness, several strategies have been adopted to update vaccines for the new SARS-CoV-2 variants, including updated mRNA vaccines (mRNA-1273.214 and CS-2034) and recombinant protein vaccine (V-01), which can induce higher immune response against Omicron variants than prototype vaccines.3–5 In this issue of The Lancet Infectious Diseases, Chijioke Bennett and colleagues6 have reported the interim results of a phase 3 study that was conducted to evaluate the safety and immunogenicity of a bivalent subunit vaccine (NVX-CoV2373 + NVX-CoV2540), which contained the spike protein of the ancestral strain and Omicron BA.5 as a heterologous booster in adults previously vaccinated with COVID-19 mRNA vaccine.6 To determine the immunogenicity of the bivalent subunit COVID-19 vaccine, Bennett and colleagues6 tested IgG and neutralising antibody levels against the ancestral strain, Omicron BA.5, and XBB.1.5. Furthermore, better immune responses are also found in CoronaVac and BNT162b2 vaccination than homologous CoronaVac vaccination, and in ChAdOx1-S and BNT162b2 than homologous ChAdOx1-S.7,10 Even though a homologous subunit vaccine strategy was not involved in the study, it was also found that the bivalent subunit vaccine as a heterologous booster significantly improved the humoral response in a population primed with the mRNA vaccine. Of note, recently, this subunit protein vaccine has been further updated to a monovalent XBB.1.5 version. vial of coronavirus vaccine on white background © Getty Images: Credit: Thanasis IF-NH has received honoraria from Pfizer, Merck, and Gilead for lectures; has offered consultative advice on COVID-19 vaccines to Fosun, Sinovac, and Sinopharm; was on the Moderna data safety monitoring board for COVID-19 vaccine 2023; has offered consultative advice on anti-SARS-CoV-2 monoclonal antibody treatment to AstraZeneca; and received support for attending meetings from AstraZeneca and Merck.