https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7142689/
Similar concerns to the above were brought up in my lectures in relation to specific vaccines (not SARS) when I was in med school, before I moved to the dark side that is.
I think one could find an interesting correlation between multiple strain- single dose vaccines vs cytokine storms, autoimmunity and death. For the non-clinically minded, skip the list of proteins, it’s heavy reading.
Let us also not forget that moving from SARS to SARS Cov 2 doesn’t naturally occur over 10 years. This mutation takes a very very long time. It was helped along.