Covid-19 Live Updates: Vaccinated People May Meet Indoors in Small Groups but Should Still Mask in Public, C.D.C. Says Syria’s leader tests positive for the virus. New York City public high schools are scheduled to reopen on March 22. nytimes

The Centers for Disease Control and Prevention on Monday issued long-awaited advice to Americans fully vaccinated against Covid-19, freeing them to take some liberties that the unvaccinated should not, including gathering indoors in small groups without precautions while still adhering to masking and distancing in public spaces.

Scientists underestimated the coronavirus — and are racing to keep up with evolution For most of 2020, scientists weren't very concerned that the coronavirus would evolve. But in a few short months, variants of the virus have become a global preoccupation -- and a potential threat to vaccines. Carolyn Y. Johnson Washington Post

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FDA authorizes new test to detect past Covid-19 infections The T-Detect COVID test, developed by Adapative Biotechnologies with help from Microsoft, was built with machine learning. Katie Palmer STAT

The Food and Drug Administration on Friday issued an emergency authorization for a new test to detect Covid-19 infections — one that stands apart from the hundreds already authorized.

A complicating factor in combating Covid hot spots: Heat Heat, environmental problems and the pandemic concentrate in certain neighborhoods. Here’s a new idea for what to do about it. POLITICO

Last summer, just as cases of Covid-19 began to surge in Southern California, so did the heat.