Ryan, thanks, no need to apologise for a lengthy response. I agree it isn’t a simple answer, but you answered fully, thanks for that, and for the reference also to Shin’s valuable article.

I haven’t read there yet, as ironically, on my current device, an old ipad, I need to convert your link to a form my device needs to follow, which happens when I repost, like this:

Why Vaccine Boosters May Not Necessarily Solve the Mutating Coronavirus Problem

So I will read now :)