A risk of rare but potentially life-threatening blood clots in combination with low platelet levels after a jab of Johnson & Johnson's Janssen COVID-19 vaccine has convinced the U.S. FDA to limit its use. The vaccine is now authorized in the U.S. only for adults who wouldn't otherwise be vaccinated and those who can't or shouldn't, for medical reasons, get another approved vaccine. Through March 18, 2022, the FDA and CDC have identified 60 confirmed cases, including nine fatal cases of the condition, called thrombosis with thrombocytopenia syndrome – a rate of 3.23 cases per million doses of vaccine administered.