The Food and Drug Administration and Centers for Disease Control and Prevention are recommending a “pause” in the administration of Johnson & Johnson’s single-dose COVID-19 vaccine to review blood clot cases.The agencies said in a statement Tuesday the CDC will convene a meeting of the Advisory Committee on Immunization Practices on Wednesday to review six cases of “a rare & severe type of blood clot” in people who received the vaccine. The FDA will then review that analysis as it also investigates the cases.”Until that process is complete, we are recommending a pause in the use of this vaccine out of an abundance of caution,” Dr. Anne Schuchat, principal deputy director of the CDC, and Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research, said in the statement.The White House said Tuesday the pause “will not have a significant impact” on the vaccine plan in the U.S.As of Monday, over 6.8 million doses of the single-dose vaccine had been administered across the country, a small portion of the 190 million COVID vaccine shots given nationwide — most of them from Pfizer and Moderna.The handful of cases the FDA and CDC are investigating occurred in women and involved a blood clot called cerebral venous sinus thrombosis, which was seen alongside low levels of blood platelets, according to their statement. Symptoms were seen 6 to 13 days after vaccination in the women, who were between the ages of 18 and 48.”Treatment of this specific type of blood clot is different from the treatment that might typically be administered. Usually, an anticoagulant drug called heparin is used to treat blood clots. In this setting, administration of heparin may be dangerous, and alternative treatments need to be given,” they said.The agencies said the “adverse events” seem to be extremely rare, but that the pause is important so that health care providers can be made aware of the reactions and properly recognize and manage the cases, given the unique treatment required.After the announcement, a growing list of states and cities announced they were suspending use of the Johnson & Johnson vaccine. Ed O’Keefe contributed reporting.