Pharma industry is a multibillion industry. Companies spend billions of dollars on multiple drug, vaccine & therapy candidates (design & discovery). So how do they ensure that they are effective and at the same time safe. The answer is by putting them under rigorous phasis of clinical research. These controlled experiments help them otain enough evidence. If successful then these candidates enter clinical .
Here is a quick summary of the different phases:
Here are a few expectations from such clinical trials: