he US Centers for Disease Control and Prevention and the US Food and Drug Administration are recommending that the US pause the use of Johnson & Johnson’s Covid-19 vaccine over six reported US cases of a “rare and severe” type of blood clot. More than 6.8 million doses of the Johnson & Johnson vaccine have been administered in the US. While officials are stressing the side effect is “extremely rare”, they want health care providers to have time to understand what potential side effects are and how to best treat them. For people who have received the Johnson & Johnson shot, those who have developed severe headache, abdominal pain, leg pain or shortness of breath within three weeks after vaccination should contact their health care provider.