What does someone's vaccination status have to do with *others* deciding to wear masks. Being vaccinated does NOT provide immunity. One can *still* catch and transmit the virus. A T could be vaccinated yet they can get infected and transmit it to their clients. Wearing a mask is for one's protection. And ought not to be dependent on other people's vaccination status.

And sorry but yes, revealing one's vaccination status IS protected health information. Just like a health professional ought not go ask that question to a patient, or if they did, said patient is NOT obligated to reveal this as, again, it is private, protected, health information.