Currently approved COVID vaccines are designed using the spike antigen derived from the ancestral strain, but health authorities are recommending changes to the vaccine strain to combat emerging variants. The goal is to ensure that next generation vaccines can tackle multiple variants of concern including the most prevalent variant for the coming season. We here discuss recent preclinical and clinical data on COVID vaccine antigens that are potential candidates for an updated vaccine.

SARS-CoV-2 variants of concern (VOC) continue to emerge, largely because some errors that are introduced during virus replication can be advantageous in regards to viral fitness and/or immune escape. One approach to tackle emerging VOCs is to focus booster vaccines on the predominantly circulating variant, which is currently Omicron¹. This would mimic what has been done successfully with vaccines based on the ancestral SARS-CoV-2 strain. However, an alternative approach could be to select an antigen that induces broad cross-reactivity to several VOCs, including the currently dominant variant. Here, we discuss preclinical and clinical evidence supporting the relevance of a booster vaccine based on SARS-CoV-2 Beta (B.1.351) spike protein and speculate on potential reasons for broad cross-reactivity of a Beta-based booster vaccine. We argue that several options for strain selection for the next booster should be considered, and that each strain option must be justified by scientific evidence.

Read more...