Which staff member should not be assigned to care for a client with herpes zoster?

When considering which staff member should not be assigned to care for a client with herpes zoster, it is critical to understand the nature of the infection and the immunity aspects associated with it. Herpes zoster, also known as shingles, is caused by the reactivation of varicella-zoster virus, which also causes chickenpox. A person who has never had chickenpox is at risk of contracting chickenpox upon exposure to the varicella-zoster virus, even if it is from a shingles outbreak, as the virus can still be transmitted.

Therefore, assigning a nurse who has never had chickenpox to care for a client with herpes zoster poses a direct risk. This nurse lacks the natural immunity that develops post-exposure to chickenpox, making them susceptible to infection.

On the other hand, the other options presented do not carry the same level of risk when it comes to transmitting or contracting the virus associated with herpes zoster. For instance, never having had roseola or mumps does not impact the nurse's risk with varicella-zoster. Additionally, while not receiving the varicella-zoster vaccine is a concern regarding immunity, the nurse’s background regarding chickenpox history remains the most critical factor in this scenario. Hence,