The number of new coronavirus cases in the United States is falling, but has the country turned a corner in the pandemic? And what kind of threats do the new variants pose to people and to the vaccine rollout?

Today, we discuss the latest in the quest to stamp out the pandemic.

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

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Background reading:

• New daily cases are starting to slow, in what some health experts see as a turning point. But they warn of a bumpy vaccination rollout amid the emergence of more contagious variants.
• The C.D.C. has eased coronavirus vaccine rules: The agency now says people can switch authorized vaccines between the first and second doses, and also extend the interval between doses to six weeks.
• One year, 400,000 coronavirus deaths: a look at how the U.S. set itself up for failure.