Apples to oranges. I have no scientific knowledge as to why certain viruses, shingles for example, do not mutate as quickly, if at all; as influenza or sars and therefore the vaccine against it protects you basically for life whereas these current shot barely last 3 months or become truly useless as new "variants" appear. That being said, the yearly "flu vaccine" is an educates guess where the pharmaceutical industry measures past virus types "performance" and then tries to predict which ones will be dominant the coming season, and base the next shot off that analysis. And another thing is that the very definition of the word vaccine has been "updated" to fit the sars shots. Those are facts that you can easily look up. It'd be interesting if you, or someone else, could provide the explanation as to why the shingles virus is one shot and done, and not sars. They're both viruses.