U.S. health officials are recommending Johnson & Johnson’s COVID-19 vaccine not be used until an investigation into cases of post-vaccination blood clots is finished. The six cases, all among women, involve a rare and severe type of clot called cerebral venous sinus thrombosis in combination with low levels of blood platelets, officials told reporters in a call on April 13. One of the patients died while a second is in critical condition at a hospital. The patients are between the ages of 18 and 48, who experienced the symptoms between six and 13 days after getting the COVID-19 vaccine. “Right now, these adverse events appear to be extremely rare,” Dr. Peter Marks, director of the Food and Drug Administration’s (FDA) Center for Biologics Evaluation and Research, said on the call. More than 6.8 million doses of Johnson & Johnson’s shot have been administered in the United States as of April 12. In response …