Here in the United States, a Food and Drug Administration advisory panel is recommending a third shot of Moderna’s COVID-19 vaccine for people 65 and older, as well as those at high risk of severe disease and workers in high-risk professions. The recommendation came even as many scientists questioned whether the protection conferred by Moderna’s vaccine is waning. Today the FDA panel will weigh whether people who’ve received Johnson & Johnson vaccines should get a second dose, and whether it might be advantageous to mix and match vaccines.