immunize against (something)
To vaccinate someone so that they become immune to a particular disease (named after "against"). A noun or pronoun can be used between "immunize" and "against." No, I never had chicken pox as a kid, so I've been immunized against it. The MMR vaccine immunizes children against measles, mumps, and rubella.
immunize someone against something
to vaccinate someone against some disease; to do a medical procedure that causes a resistance or immunity to a disease to develop in a person. They wanted to immunize all the children against the measles. Have you been immunized against polio?