A Chosen One with a Doctor skill of at least 75% can speak with Dr. Troy in a dialogue option to introduce themselves as a fellow physician curious about the much-vaunted Vault City medical methods, leading to the cost-free accrual of the Vault City Training perk. Returning with an active Poison or Radiation counter level and asking him to cure either will then enable the derivative Vault City Inoculations perk as well.
Troy can heal if the player character have been made a citizen of Vault City. He will heal the entire party if talking to a Captain of the Guard.