That makes sense. But surely a factor is also what you’re actually changing? If the vaccine is exactly the same in terms of overall compound and delivery and all that is being tweaked is the “signal” then that’s very different to any fundamental change needed. A bit like do you just need to turn the dial to find a new radio station, or do you need to change the actual radio. Sorry best example I could think of
Its how the drug approval regulatory authorities will react. This is a fairly unique situation. Flu vaccines are a good analogy as we tweak them regularly.
Covid vaccines use different mechanism. The Sinopharm, sinovac use the whole virus (in an inactivated form). The mRNAs Moderna and Pfizer use the mRNA which causes production of spike protein in cells for immune system to recognise. And others like Astrazeneca use a weakened common cold virus as a vector to introduce the spike protein as the immunogen.
For me the single unifying theme across all of the covid vaccines is how remarkably safe they've been, with variable efficacy. That's pretty much proof of concept, for me, that utilising the spike protein (regardless of what mutations its got) is a safe, if variably effective, way of vaccinating against SARS-COV2. Whether the MHRA, FDA, EMA sees it the same way I don't know. I think a basic phase I,II type safety trial with volunteers for reactogenicity should suffice but who knows
Vaccines have different preservative ingredients that are fairly static and there's some patients who have allergic reactions to but these are known and managed with avoiding said ingredients if possible and giving vaccines after consulting with allergy specialists and with anaphylaxis kits everready (which to be fair they are in most vaccine centres)