Phase 2, Phase 3, Phase 4

Hi - the thread is becoming a little boring so  I went on to Merck's website and had a look at their definitions of Phase 2, 3 and 4...

Phase 2: Phase 2 clinical trials test the vaccine or medicine in approximately 100 to 500 volunteers. In the case of medicines, volunteers usually have the disease or condition the investigational medicine is designed to treat. In vaccine studies, the volunteers are usually healthy. The goals of this phase are to determine:

• How well the medicine or vaccine works
• If the medicine or vaccine is safe
• If there are any side effects
• How much of the medicine or vaccine is needed and how often

Phase 2 trials can take from six months to one year or more to complete.

Phase 3: Phase 3 clinical trials can test the medicine or vaccine in 1,000 to 5,000 patient volunteers. For medicines, volunteers have the disease or condition the medicine is designed to treat. In vaccine studies, the volunteers may be healthy or have diseases or conditions. Phase 3 trials take place in hospitals, clinics or physician offices. Researchers closely monitor patients at regular intervals to:

• Confirm that the medication or vaccine is effective
• Identify and monitor side effects
• Compare the medicine or vaccine to commonly used treatments

Phase 3 trials can take from one to four years to complete, depending on the disease, length of study and the number of volunteers.

Phase 4 or On-going trials: Phase 4 clinical trials are conducted after the medicine or vaccine has been approved by the appropriate government and regulatory agencies and is being marketed. Researchers continue to gather information about the medicine or vaccine and its safety, side effects and effectiveness.
Marketed products also are studied for new indications. Thousands of people usually participate in ongoing trials

Given the numbers of patients required for a Phase 3 study to be completed, it would seem a large target (1,000 - 5,000 patients) for Phase 3 and up to 4 years?  Seems like we are a far way from that thoughts?