Virus antigenic evolution is not the same thing as bacterial antibiotic resistance. Intuitions from one may not apply to the other, for a variety of reasons

One of many reasons they can differ is articulated in this elegant theory paper by @dkenned11 and Andrew Read: antigenic natural selection typically (though not always) act on less diverse pathogen populations than drug therapy

https://doi.org/10.1098/rspb.2016.2562

Another important difference: much easier to update vaccines (especially mRNA vaccines) after antigenic change than to develop new antibiotics (or antivirals, for that matter) after the evolution of drug resistance

And perhaps most importantly: antigenic evolution will not necessarily make you completely "naive" to a pathogen you've seen before. You'll be less protected against *any* symptomatic disease, but you could still be very well protected against severe disease

Addendum: https://twitter.com/dylanhmorris/status/1345856689854148608