[bonzini]

> Replicant viruses do not carry the spike protein, they don't contribute to antigen protection.

Are you sure? Do you mean that all of them must have had recombination that added the E1 gene and dropped the spike protein?

[sudosysgen]

Indeed. So if a virus is able to replicate it must have a replication-competent E1 gene which normally encodes for the spike