U.S. regulators approved a third coronavirus vaccine in February, giving the country another badly needed tool at a critical time in the pandemic.

The greenlit vaccine, made by Johnson & Johnson, requires only a single shot. It’s easy to use, ship and store, and it did not cause any serious side effects during clinical trials. The nation’s leading medical experts cheered its authorization and urged people to take whichever coronavirus vaccine is available to them.

“You now have three highly efficacious vaccines, for sure, there’s no doubt about that,” Anthony S. Fauci, the nation’s top infectious-disease expert, said the day after the Food and Drug Administration authorized the Johnson & Johnson vaccine. “I think people need to get vaccinated as quickly and as expeditiously as possible.”