The Collaborative International Dictionary of English v.0.48:

Vaccinator \Vac"ci*na`tor\, n.
   One who, or that which, vaccinates.
   [1913 Webster]

WordNet (r) 3.0 (2006):

vaccinator
    n 1: a medical practitioner who inoculates people against
         diseases [syn: inoculator, vaccinator]