> A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. While most are prophylactic, it

> A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. While most are prophylactic, it's not a requirement to be considered a vaccine. Vaccines are not "meant to prevent a disease". They're meant to provide immunity to the disease, whether that be before (prophylactic/prevention) or during (therapeutic/treatment).