My current take (not a virologist, doctor): At this point, if you are not immunocompromised and you have the first vaccination and a booster. You should be able to easily recover regardless of the mutation(s). The virus would need to completely diverge from SARS-CoV-2 in order to fully defeat the countermeasures of the current vaccinations.
Narrowness of immune response: >The mRNA and viral vector vaccines induced ONLY spike protein antibodies in the inoculated test subjects >In comparison, whole inactivated virus and natural infection induce antibodies to many parts of the virus Original antigenic sin: >Subjects injected with the old formulations have locked their immune response to only a few antibodies >Any new formulation of the injection will ampli…
The mRNA vaccines also induce the cell-mediated immunity, unlike e.g. subunit vaccines that only consists of a protein. The cell-based response is fundamentally different and not based on the 3D structure of the virus protein like the antibody response. So mutation that would evade the antibody response would not automatically evade the cell-based response as well.
The spike protein is also the most important protein of the virus. And antibodies are mostly useful against surface components of the virus, not so much against stuff that's on the inside. The spike protein performs a critical function, to evade the antibody response it has to do both, change enough to be unrecognizable while still being able to infect cells with a similar efficiency. That's not an easy thing to do.