Here is what WebMD says at
https://www.webmd.com/skin-problems-...es-myths-facts
"The open blisters of the rash can’t pass on shingles, but they can spread the chickenpox virus to someone who’s never had it. And that can lead to a later shingles outbreak."
Also at
https://www.webmd.com/skin-problems-...hingles-skin#2
"Is Shingles Contagious?
Yes. You can spread the varicella zoster virus to people who’ve never had chickenpox and haven’t been vaccinated.
You’re contagious until all of the sores have crusted over. Until then, avoid
pregnant women who may not have had chickenpox or the
vaccine, people with weak immune systems, and newborns."