Some health experts think the United States should follow suit. Dr. Ezekiel J. Emanuel, a co-director of the Healthcare Transformation Institute at the University of Pennsylvania, has proposed that for the next few weeks, all U.S. vaccines should go to people receiving their first dose... Dr. Emanuel argued that Britain’s campaign to get first doses into more people had played a role in the 95 percent drop in cases since their peak in January. “It’s been pretty stunning,” Dr. Emanuel said. He points to data like this as further evidence that the United States should stretch out vaccinations. He and his colleagues estimate that if the country had used a 12-week schedule from the start of its rollout, an additional 47 million people would have gotten at least one dose by April 5. Sarah E. Cobey, an epidemiologist and evolutionary biologist at the University of Chicago, said she thought that the United States had lost a precious opportunity to save many lives with such a strategy. “We’ve missed a window, and people have died,” she said.