A nurse who refused to wear a surgical mask after receiving an exemption from a mandatory flu vaccination was fired for violating her hospital's policy. Carla Brock, a board-certified holistic nurse who has worked 11 years at Cox South Hospital here, said she is speaking out because she believes her hospital's new requirement to wear a mask if a staffer opts out of the flu vaccine amounts to a scarlet letter. CoxHealth, which owns four hospitals in southwest Missouri and northwest Arkansas, says it simply is putting the patient first.