The U.S. Food and Drug Administration authorized Johnson & Johnson’s COVID-19 vaccine Saturday. It is the first single-dose COVID-19 vaccine available in the U.S., and is one that “checks nearly all the boxes.”With more than 28.4 million confirmed COVID-19 cases in the U.S. and nearly 511,000 reported deaths since the start of the pandemic, and while the demand for vaccine still far exceeds supply, these