WASHINGTON (AP) — COVID-19 vaccine makers told Congress on Tuesday to expect a big jump in the delivery of doses over the coming month, and the companies insist they will be able to provide enough for most Americans to get inoculated by summer.

Vaccinations got off to a rocky start, but by the end of March, Pfizer and Moderna expect to have provided the U.S. government with a total of 220 million vaccine doses, up sharply from the roughly 75 million shipped so far.

"We do believe we're on track," Moderna President Stephen Hoge said, outlining ways the company has ramped up production. "We thin...