4 phases of COVID-19 vaccine clinical trials explained | USA TODAY

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COVID-19: What are the 4 phases of vaccine clinical trials?
RELATED: Dr. Anthony Fauci’s latest testimony https://youtu.be/X7ks62Jtvn0

Approving a vaccine in the U.S. usually takes years, but COVID-19 vaccines are moving through in record time. What does that mean?

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