Drug makers Moderna and Pfizer announced this week that early test results show their respective COVID-19 vaccines to be more than 90% effective. Now, both are on track to request emergency authorization from the FDA. But even as scientists race to roll out a vaccine, there are questions about the diversity of the test subjects. Soledad O’Brien speaks with Dr. James E. K. Hildreth, one of the nation’s leading immunologists and head of the Meharry Medical College in Nashville.



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