US recommends ‘pause’ for single-dose Johnson & Johnson COVID-19 vaccine to investigate clotting reports.

The Centers for Disease Control indicated in an alert Tuesday that the Johnson & Johnson vaccine could resume as soon as Wednesday. The alert came after a chaotic day when the Food and Drug Administration recommended there be a “pause” for the vaccine, leading virtually every state to halt use of the single-dose shot.

The CDC’s Advisory Committee on Immunization Practices will convene Wednesday for an emergency session, with a vote scheduled on “updated recommendations for use” before the group adjourns at 4:30 p.m. ET.

Dr. Anthony Fauci, President Biden’s chief medical adviser, told “CBS Evening News” anchor Norah O’Donnell on Tuesday night that it appeared that the adverse effect occurred within six to 13 days, and “so if you’ve had it a month or two ago, I think you really don’t need to worry about anything.”

Fauci emphasized that the chance of these adverse side effects is “less than 1 in a million,” but he said to be alert to the symptoms such as severe headache, some difficulty in movement — such as in a neurological type of a situation — or some chest discomfort and difficulty breathing.

As of Monday, more than 6.8 million doses of the Johnson & Johnson vaccine had been administered across the U.S., a small portion of the overall 190 million COVID vaccine shots given nationwide — most of them from Pfizer and Moderna.

The White House said Tuesday that the pause “will not have a significant impact” on the nationwide vaccine plan. President Biden assured Americans that he had made sure the U.S. has enough vaccine doses for all American adults from Pfizer and Moderna alone.

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 six 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.

Ed O’Keefe contributed to this report.