The CDC is looking into at least six cases of rare but serious blood clots in women under the age of 50 who got the Johnson and Johnson covid-19 vaccine. Experts say they need more evidence to decide whether the clots were linked to the vaccine, and how big the risk is. A CDC advisory panel will meet in the coming weeks to continue discussions. For more, we spoke to Professor Peter Pitts, Founder, Center for Medicine in the Public Interest and Former FDA Associate Commissioner.