Final answer:
The correct term for a vaccine containing the fully virulent form of the disease-causing agent is a live virulent vaccine, which is a weakened version of the virus designed to elicit immunity without causing severe disease.
Step-by-step explanation:
The term that best defines a vaccine containing the fully virulent form of the disease-causing agent is live virulent vaccine. Live virulent vaccines are made from a weakened or attenuated form of the pathogen that causes the disease. They are designed to still cause infection but are significantly weakened so they do not produce major disease, allowing the immune system to develop a response to prevent future infection. These types of vaccines do carry a risk of reverting back to a virulent form through mutations, also known as back mutations, which can then lead to disease.