Prevention trials, implemented to reduce or delay progression to overt disease in a population at risk to the disease, are an important approach to health promotion.
Therapies shown to reduce disease severity in patients with a specific disease are obvious, but not the only, candidates for a prevention trial in populations at high risk for prevalent diseases (such as heart failure, diabetes, COPD, asthma in children).
These trials clearly require access to public funding. Commercial companies cannot be expected to support prevention trials, unless they are evaluating a therapy they have developed specifically to prevent or slow a disease process. This approach is clearly within the NHLBI (NIH) mandate.