Federal authorities on Tuesday recommended that states stop using Johnson & Johnson’s Covid-19 vaccine while an investigation is conducted into six rare but serious cases of clotting problems that were reported among women who received the vaccine. The clotting issue is similar to the one reported after use of AstraZeneca’s Covid-19 vaccine, which has not been authorized for use in the United States to date. And it is similar to an event that occurred during Johnson & Johnson’s U.S.-based clinical trial, an event that led to a temporary pause in that trial. The CDC and the FDA jointly announced the recommendation, which falls short of an order not to use the vaccine. The statement said a special meeting of CDC’s Advisory Committee on Immunization Practices will be held Wednesday to review the data around the issue.