Hospitals, state health departments and the federal government are racing to decide how to use up millions of Johnson & Johnson ’s Covid-19 vaccine doses that are set to expire this month. The prospect of so many doses going to waste in the U.S. when developing nations are desperate for shots would add pressure on the Biden administration to share stockpiled vaccines. But there are few practical solutions to administering them quickly in the U.S. or distributing them in time to foreign countries, according to those involved in the vaccination drive.