The U.S. could soon be giving at least a million COVID-19 vaccinations a day despite the sluggish start, Dr. Anthony Fauci said Tuesday, even as he warned of a dangerous next few weeks as the coronavirus surges.

The U.S. gave the final go-ahead Friday to the nation’s first COVID-19 vaccine, marking what could be the beginning of the end of an outbreak that has killed nearly 300,000 Americans, according to a person familiar with the decision but not authorized to discuss it publicly.