[CydeWeys]

Good news is that COVID (and coronaviruses in general) don't seem to have the same kind of mutation potential to bypass immune system responses like influenza does. So our best guess is that a COVID vaccine will be like Tdap or MMR, i.e. after the initial course you maybe only need occasional booster shots (if even that), vs influenza where it mutates enough that a new vaccine must be developed and administered every year.

[Gibbon1]

Not widely enough understood. Influenza is a segmented virus and generates new strains by reassorment. Where two different strains of influenza infecting a cell shuffle their RNA segments to produce a third strain.

Best to think of influenza as an ever shifting and recombining family of viruses.

Covid19 has a single strand of RNA and doesn't do that.