You can rescind any form of medical consent, including vaccine consent forms. However, you must do so before you receive the treatment. While it is not typically advisable, it is within your rights to refuse future inoculations if that is what you choose. All consent forms have terms for removing permission. For some, it is a one-time permission, and for others, the consent is active until you submit a form in writing to remove that permission. If you are uncertain which one applies, ask or simply submit a written retraction.