Clinical trials are prospective research studies on human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments, vaccines, or medical devices. In the case of a trial evaluating the clinical potential of a novel drug- or a vaccine candidate, the procedure typically involves the generation of detailed safety and efficacy data. Clinical trials consist of at least 3 phases. Occasionally a fourth phase might be necessary if the healthcare authorities think the medicine can be improved or if the manufacturer has to answer specific questions from the regulatory authorities. Before a clinical trial can be initiated and start enrolling patients, it needs health authority and ethics committee approval.