For new strains, yes, the Pfizer and Moderna (and other as yet unlicensed mRNA) vaccines will cover you more or less perfectly well. When scientists speak of strains they’re referring to variations in the virus that still keep it within the same serotype, the mRNA vaccines will work to produce antigens for the entire serotype.Mmm, no Irailfan, the currently offered vaccines, certainly those from Pfizer and Moderna are mRNA based vaccines, so far there are no strains of COVID known to bypass antibodies produced following these vaccinations.Fair enough, I don't know how many strains of this thing there will eventually be, so are you more or less saying whatever strain comes out, the current vaccines will prove effective? (just asking).
Microbiology and genetics are not my primary area of expertise, so I am going to grossly over simplify the following so as to not lose myself and others in the strict details.
Should SARS-CoV-2 move beyond new strains and morph into new serotypes so this would mean variations like we see in Influenza A so these are the H1N1, H3N2, H18N11 (the latter only exists in bats) etc which you sometimes read about in ‘flu season’, then a specific mRNA vaccine for one of those would not protect you from the others.
The ‘good news’ is that mRNA vaccines are ‘relatively easy’ to convert to cover new serotypes, which is why we are relatively good at producing decent Influenza A vaccines relatively quickly as required for new serotypes.