PHILADELPHIA (AP) — An aborted effort to vaccinate Philadelphia residents against the coronavirus raises larger questions about the health care system in the city and nationwide. City officials made an unusual choice when they picked a 22-year-old graduate student to run a large vaccination site. Andrei Doroshin says he and his friends created an online registration site, leased a convention center and lined up practitioners. But questions soon arose about whether he planned to sell patient data, and the city shut the site down. Thousands of people who hoped to get the vaccine are now scrambling to find new appointments.