Did you have chicken pox as a child?
If yes, you are immune to chicken pox.
Do you need a blood test to confirm that?
Should you take a chicken pox vaccine?
Use common sense.
If you had it, you are immune.
That is how viruses work.
The problem with Corona viruses is that they are (to use my term) slippery. In other words they shift rather easily.
Chicken pox is very stable. Cold and flu viruses not so much.
Of course, that holds true with the jab also.
A bunch of people (kids?) got chicken pox a couple/three (?) years ago, even though vaxed. If adults get the c.pox it can be very serious; if children get it, some days of feeling icky and then over. I don’t see the need for almost all vaxes.