In a nutshell, the current medical criticism about the mRNA and adenovirus vaccines is that your body ends up making dominant long-term antibodies against the very specific coronavirus variant of the spike proteins. These long-term antibodies “muscle out” your body’s short term antibodies that are capable of attacking all coronaviruses, not just COVID. It’s leaves your body a bit defenseless against other variants.

This is why during the animal trials of previous mRNA vaccines all the animals died when exposed to wild coronaviruses or other variants.