And now for a new and vexing dilemma for states trying to vaccinate their residents against Covid-19: What to do when supply of the vaccine greatly outstrips demand?
Several states, long desperate for as many doses as they could get, are now awash in unused doses of Covid vaccines as demand dwindles and supply continues to ramp up.
About 112.6 million people, or 34 percent of the population, were fully vaccinated as of Saturday.
During the initial rush of vaccine distribution over the winter and into the spring, appointments were coveted and often difficult to find.
Of the 329 million doses shipped by the federal government to states, about 257 million have been administered, according to the Centers for Disease Control and Prevention.
Centers for Disease Control