So far our family has been free from the dreaded chickenpox, although
I intend to get my titres checked as I understand I have never had a
clinically apparent dose.  My breastfed son (now 10yo and long
weaned) has been exposed several times, but never caught it.

A friend's 12mo breastfed baby got quite a bad case, shortly after
his 3yo sibling. Mother had had it as a child.  The sores in her
baby's  nappy area became infected and he was in a mess, so she
treated them with breastmilk.  They healed fast, with no scarring!
Other less severe and not infected spots took longer to heal and
left marks, although these eventually faded after a long time.  Did
the chickenpox antibodies in her milk help healing, or was it just
the wonderful milk itself.  She regrets she did not use it on both
her kids, on all their spots.