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Table 1 Descriptions of Research Studies and Clinical Trials

From: Strengthening capacity for AIDS vaccine research: analysis of the Pfizer Global Health Fellows Program and the International AIDS Vaccine Initiative

Study Description
Observational study A study where researchers are learning about HIV/AIDS without actually testing a drug or other intervention. Such a study might involve drawing blood from trial participants over time, to understand characteristics of non-infected individuals and to observe what happens at the cellular level when they become infected.
Pre-clinical trials Studies of vaccines or treatment which are carried out in animals.
Clinical trials
Phase I Researchers test a vaccine in a small group of people (20–80) to determine how a drug should be given, how many doses are needed, and whether it is safe
Phase II Experimental vaccine is given to a larger group of people (100–300) to see if it is effective and to further evaluate its safety
Phase III Experimental vaccine is given to large groups of people (1,000-3,000) to confirm its effectiveness, monitor side effects, and compare to commonly used treatments.
Phase IV Post-marketing studies determine a drug’s risks, benefits, and optimal use.
  1. Source: http://clinicaltrials.gov/ct2/info/understand.