CDC scientists say their investigation into a rare blood clotting issue linked to the Johnson & Johnson Covid-19 vaccine has identified 28 people who developed the potentially life threatening blockages — three of whom have died. The FDA and CDC on April 13 asked states to temporarily halt using J&J’s vaccine “out of an abundance of caution” while it investigated six women, ages 18 to 48, who developed cerebral venous sinus thrombosis, or CVST, in combination with low blood platelets within about two weeks of receiving the shot.