The Food and Drug Administration authorized Pfizer’s Covid-19 vaccine for emergency use on Friday, clearing the way for millions of highly vulnerable people to begin receiving the vaccine within days.

The authorization is a historic turning point in a pandemic that has taken more than 290,000 lives in the United States. With the decision, the United States becomes the sixth country — in addition to Britain, Bahrain, Canada, Saudi Arabia and Mexico — to clear the vaccine. Today, we ask the science and health reporter Donald G. McNeil Jr. what might happen next.

Guest: Donald G. McNeil Jr., a science and health reporter for The New York Times.

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Background reading:

• Pfizer has a deal with the U.S. government to supply 100 million doses of the vaccine by next March. Under that agreement, the shots will be free to the public.
• The vaccines are on their way, but experts still say a difficult winter of coronavirus infection and death lies ahead.

For more information on today’s episode, visit nytimes.com/thedaily