WASHINGTON (AP) — President Joe Biden said Tuesday that the U.S. expects to take delivery of enough coronavirus vaccines for all adult Americans by the end of May, two months earlier than anticipated, as his administration announced that drugmaker Merck & Co. will help produce rival Johnson & Johnson’s newly approved shot.With the bolstered supply, Biden also announced he would be using the powers of the federal government to direct all states to prioritize vaccinating teachers, and said the federal government would provide the doses directly through its pharmacy program.