According to the National Institutes of Health, a clinical trial is "a research study to answer specific questions about vaccines or new therapies or new ways of using known treatments." These studies allow researchers to determine whether new drugs or treatments are safe and effective. When conducted carefully, clinical trials can provide fast and safe answers to these questions.

Ideas for clinical trials usually originate with medical researchers. After researchers have tested new therapies or procedures in their own laboratories, they begin planning first-phase clinical trials if the new therapies or procedures seem to hold promise. Tests on humans are carried out only if laboratory and animal studies show promising results.

Clinical trials must adhere to a set of rules called protocols. The protocols define the requirements for participating in the trial; the schedules of tests, procedures, medications, and dosages; and the duration of the study...