"Variant" is the correct (scientific) wording - these are not "strains" or "mutations", the number of changes in the virus RNA is not high enough. The fearmongering that there is no immunity against SARS-CoV-2 started from day one, it all was and is a lie. The virus doesn't change fast enough to escape acquired immunity (through infection or vaccination) in the next 10 years. Otherwise, we would see millions of reinfections, like with the seasonal viruses.