To be dispensed in the United States, vaccines have to go through the same sorts of FDA-mandated clinical trials as other pharmaceuticals. As vaccine development progresses, there are various internal tests, and then animal testing. Then there are three phases of human trials. Phase I tests safety. Phase II tests various dosage levels for safety and effectiveness. Phase III tests the actual effectiveness of the drug or vaccine on a large enough cohort of human subjects to allow for variations in response, factoring in considerations such as how the vaccine affects children, teens, persons over
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