Which of the following situations would require informed consent?

Informed consent is a crucial ethical and legal requirement in healthcare, ensuring that patients or their guardians understand the risks, benefits, and alternatives of a medical procedure before agreeing to it. In the case of elective surgery, the process typically involves a thorough discussion between the healthcare provider and the patient regarding potential risks, expected outcomes, and alternatives. This dialogue is essential in allowing the patient to make an informed decision about their care.

In elective surgery, unlike emergency procedures or routine checks, it’s imperative that the patient comprehensively understands what they are consenting to. This contrasts with situations like emergency surgery on a minor, where immediate action is necessary for the patient's health and informed consent may not be feasible. Importance also rests on cases such as routine blood pressure checks, which do not typically require extensive consent discussions, as they are low-risk procedures. Lastly, administering a vaccine without parental knowledge raises ethical concerns and typically does not comply with the informed consent requirement, as it lacks the necessary discussion and understanding about the treatment being provided.

Thus, the correct choice represents a scenario where informed consent is not just recommended but vital to ensure that the patient is fully aware and agreeable to the procedure they are undergoing.