Vaccine, page-5

New strains of flue virus happen every year. The flu vaccine needs regular revision.That's a major reason for repeat vaccination each year.
This virus (SARS COVID2) has a more stable genetics than influenza but is still RNA genetics which is liable to change over time, Of course, if a generic vaccine can be made for any corona group virus, then maybe new strains of SARS COVID2 will not need dealing with later.