The distribution of vaccines in the United States has gotten off to a slower-than-expected start, federal health officials acknowledged in a news conference on Wednesday, though they also voiced confidence that the pace would accelerate in the coming weeks. As of Wednesday, more than 14 million doses of the Pfizer and Moderna vaccines had been sent out across the United States, up from 11.4 million doses on Monday morning. But just 2.1 million people had received their first dose as of Monday morning, according to a dashboard maintained by the CDC. “