I wish to investigate how a virus could be attenuated through targeted mutagenesis by investigating the protein mutations in order to produce an efficacious vaccine. Are there examples where the protein sequence of exisiting vaccine strains have been compared against their wild-type counterparts to understand the mechanism of virulence/attenuation? Secondly which viral proteins are the focus of such studies? I am a computer scientist looking for a mathematical approach towards understanding the mutational parameter space of viral proteins sequence data, for example through a mutational correlation matrix between vaccine and wild type protein sequence. This may have application for example to COVID-19.