Some therapies are not developed in the same manner as drugs, such as disease prevention therapies, vaccines, biologicals, surgical techniques, medical devices, and diagnostic agents.
Prevention trials are conducted in:
- healthy individuals to determine if the therapy prevents the onset of disease,
- patients with early-stage disease to determine if the therapy prevents progression, or
- patients with the disease to determine if the therapy prevents additional episodes of disease expression.
Vaccine investigations are a type of primary prevention trial They require large numbers of patients and are very costly because of the numbers and the length of follow-up that is required.
The objective of a diagnostic or screening trial is to determine if an agent can “diagnose” the presence of disease. Usually, the agent is compared to a “gold standard” diagnostic that assumed to be perfectly accurate in its diagnosis. The advantage of the newer diagnostic agent is less expense or a less invasive procedure.