The Johnson & Johnson Janssen VaccineStephen Zenner | LightRocket | Getty ImagesCDC 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 Food and Drug Administration and Centers for Disease Control and Prevention 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. They recommended resuming use of the shot ten days later after the CDC determined that the benefits of the shots outweighed their risks. CVST is a form of thrombosis with thrombocytopenia, or TTS, which are blood clots with a low platelet count that puts patients at risk for stroke. Platelets actually help the blood to clot.CDC official Dr. Tom Shimabukuro said Wednesday that four of the 28 people with TTS remained in the hospital as of May 7, one of whom was in the ICU, and two have been discharged to a post-acute care facility. The remaining 19 patients have all been discharged, he said during a presentation to the CDC’s Advisory Committee on Immunization Practices. The panel voted earlier in the day to recommend the Pfizer-BioNTech vaccine for use in 12- to 15-year olds. The median age of the patients with TTS was 40, ranging from 18- to 59-years old. Women who were 30- to 39-years old accounted for the biggest risk group. All of the patients received the J&J shot before the pause on April 13. Out of the 28 TTS cases, 19 affected the brain with ten of those patients suffering from a cerebral hemorrhage, he said. The other clots formed in the lower extremities, pulmonary arteries or other areas of the body.