Shots cause pain in two ways: a momentary pinch from piercing the skin and a muscular ache that can last for days. In May, the FDA approved a device that releases flu vaccine directly into the skin, avoiding the muscles (and the ache) altogether. The Fluzone Intradermal microinjector's needle is about a tenth as long as the needle on a regular syringe and the width of a human hair. And because there are more immune cells in skin than in muscle, doctors could use less vaccine per shot, which could decrease vaccine shortages. The device's manufacturer, medical company Sanofi Pasteur, says it will start shipping it in the U.S. this fall, just in time for flu season.