The impact of authority figures on others has long been a central topic in psychological research. Numerous studies have demonstrated that authority not only enhances persuasive power but can also lead individuals to comply in troubling or irrational ways. In medical settings, authority is embodied by healthcare professionals whose goal is to improve patient health. However, patients do not always perceive doctors or nurses as authoritative figures. At times, they may place greater trust in individuals lacking medical expertise but who confidently disseminate misinformation—such as false claims about the dangers of vaccines or advocacy for “natural living” practices that discourage vaccination. This chapter also explores the ethical tension between encouraging vaccination and upholding patient autonomy and the right to self-determination. It presents psychological research related to these challenges and offers practical guidance for healthcare professionals on how to engage effectively and respectfully with patients.