(AP) – Health officials say they believe the “vast majority” of cases in the U.S. vaping illness outbreak have been tied to vitamin E acetate. That’s a thickening agent added to illicit THC vaping liquids.áOfficials also said Friday that vaping illnesses can get worse, even deadly, after patients leave the hospital and doctors should check on patients within two days of sending them home. The nation’s outbreak of vaping-related lung injuries continues. But new cases are on the decline. More than 2,500 cases have been reported across the nation. There have been 54 deaths.