why is signing a waiver necessary?...

Question: 

why is signing a waiver necessary?

Answer: 

From your question, it is not clear which waiver you have been asked to sign. Please speak with the health care provider who gave you the waiver with any questions.

You may be referring to a vaccine consent form. It is the professional and legal responsibility of health care providers to obtain informed consent (permission) prior to immunization. Depending on the health care provider and location of the service, consent may be provided verbally or in writing. The health care provider must assess you can legally consent to or refuse immunizations, that you are able to understand  the benefits and possible reactions for each vaccine, and the risks of not getting immunized, 

ImmunizeBC Nurse