The studies each aim to enroll 30,000 people and determine whether the vaccines are safe and effective
The headquarters of the biotech company Moderna in Cambridge, Mass., on May 19, 2020. The first large study of safety and effectiveness of a coronavirus vaccine in the United States began on Monday morning, July 27, 2020, according to the National Institutes of Health and Moderna, which collaborated to develop the vaccine. (Tony Luong/The New York Times)
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