Have no idea - but ultimately I have decided the vaccine is no longer worth the risk. I suspect that a large percentage of people have came to similar conclusions based on the percentage seeking out the next generation of vaccines.
When it first came on the scene - it was much more severe and the chances of an unproven vax were worth the risk of minimizing the symptoms. As it has made the rounds a few years now and the number of severe cases has dropped - it's becoming clearer it's more of a "nuisance" virus for most rather than a severe disease. I did get it pretty bad about 18 months ago - took me off my feet for a day and a half.
Had it about 3 years ago after a cruise - one of the first cruises they did following the shutdown - wasn't fun, but wasn't any worse than any flu I've had.
Also suspect it is what likely did my mom in - officially was a heart attack - but this was late 2020 and she was in a nursing home dealing with progressing Parkinson's - honestly, heart attack was the easiest way to go - no pain, no long drawn out hospital stay - just passed peacefully one night. The nursing home of course would never say COVID and because it happened NYE - the coroner didn't even start an inquist until 5 days later and again wasn't about to say COVID or relate in any way to the shot she had just received a day earlier.