The US reaches 25 million cases of Covid-19. Now it's a race between vaccines and variants. / CNN

The White House restricts entry of non-US citizens from the UK, South Africa, and Brazil, where new Covid strains have emerged. / CNBC

Why scientists are more worried about the Covid-19 variant discovered in South Africa: its effects on vaccines. / Vox

Moderna says its vaccine is effective against the new variants, but it’s developing a new form that could be used as a booster shot. / The Washington Post

Helen Branswell answers questions on the vaccine rollout, who can get doses, and side effects. / STAT

One explanation for why some long-haulers aren’t recovering: “even if they test negative, they may in fact still harbor a Covid infection somewhere in their body.” / The New York Times Magazine

Partisan lines are hardening in the Senate over the impeachment fate of President Biden’s predecessor. / The Wall Street Journal

Related: All your impeachment questions answered. / Wake Up to Politics

The intelligence community is buying location data from smartphone apps to track Americans’ movements without a warrant. / The Daily Mail

Some 3,500 people were arrested as police tried to shut down rallies across Russia in support of Alexei Navalny. / The Guardian

China overtakes the US as the world's top destination for new foreign direct investment. / BBC News

The current fighting in Darfur is said to be the world’s first climate change conflict. / Brookings

Roy Scranton: We all want a “new normal.” That’s not in the forecast. / The New York Times

Joan Didion on enduring the pandemic: “I miss having my friends to dinner. On the other hand, my wine bills have gone down.” / TIME

The Miami Heat plan to use coronavirus-sniffing dogs to screen fans who want to attend games. / ESPN

“She had a particular hatred for the old and weak.” An obituary for a no-good, grumpy dog. / Boulder Beat

The approximate size of various ocean creatures with a mitten-ed Bernie Sanders for scale. / Twitter

A realizable goal for 2021: cooking less. / Bon Appétit