It’s been almost a year since the World Health Organization declared the coronavirus outbreak a pandemic.And the virus is persisting: A downward trend in the U.S. caseload has stalled, and concern about the impact of variants is growing. Yet inoculations are on the rise, and the F.D.A. has approved Johnson & Johnson’s single-dose vaccine, the third to be approved in the U.S.Today, we check in on the latest about the coronavirus. Guest: Carl Zimmer, a science writer and author of the “Matter” column for The New York Times.    Sign up here to get The Daily in your inbox each morning. And for an exclusive look at how the biggest stories on our show come together, subscribe to our newsletter. Background reading: After the Johnson & Johnson vaccine approval, President Biden vowed that there would be enough vaccine doses for “every adult in America” by the end of May.For more information about the emerging mutations, check out The Times’s variant tracker. For more information on today’s episode, visit nytimes.com/thedaily. Transcripts of each episode will be made available by the next workday.