Federal health officials called for a halt in the use of the company’s coronavirus vaccine while they study serious illnesses that developed in six American women.

WASHINGTON — Injections of Johnson & Johnson’s coronavirus vaccine came to a sudden halt across the country on Tuesday after federal health agencies called for a pause in the vaccine’s use as they examine a rare blood-clotting disorder that emerged in six recipients.

All six were women between the ages of 18 and 48, and all developed the illness within one to three weeks of vaccination. One woman in Virginia died, and a second woman in Nebraska has been hospitalized in critical condition.

More than seven million people in the United States have received Johnson & Johnson shots so far, and another 10 million doses have been shipped out to the states, according to data from the Centers for Disease Control and Prevention.

“We are recommending a pause in the use of this vaccine out of an abundance of caution,” Dr. Peter Marks, the director of the Food and Drug Administration’s Center for Biologics Evaluation and Research, and Dr. Anne Schuchat, the principal deputy director of the C.D.C., said in a joint statement. “Right now, these adverse events appear to be extremely rare.”









While they framed the move as a recommendation to health practitioners, the impact was immediate. By Tuesday evening, every state, the District of Columbia and Puerto Rico had announced a pause in Johnson & Johnson vaccine injections.

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The same went for the U.S. military, federally run vaccination sites, and CVS and Walgreens, two pharmacy giants that participate in the federal program, officials said. Rite Aid, Walmart and Publix also announced that they had paused Johnson & Johnson injections.

Beyond American shores, Johnson & Johnson said it would delay the rollout of its vaccine in Europe, where several countries were poised to start administering it this week. South Africa, devastated by a more contagious variant of the virus that emerged there, also suspended use of the vaccine. Australia announced it would not purchase any doses.

The Biden administration tried to portray itself as well prepared for the setback. President Biden said he would meet his goal to have enough doses to vaccinate every American adult who wanted it by the end of next month.

The reaction prompted an intense debate among public health experts about whether guarding against such a rare disorder was worth the cost. Scores of vaccine appointments were canceled this week, and some public health officials feared that by fueling vaccine hesitancy and conspiracy theorists, the pause could prompt fewer Americans to get vaccinated — and expose them to far more risk.

Others said the F.D.A. and the C.D.C. simply had no choice.

“It’s incredibly challenging, but to ignore it would have been worse,” said Rachael Piltch-Loeb, an expert in health risk communication at the N.Y.U. School of Global Public Health. If the public suspected that the government was concealing serious potential side effects, she said, far more people might decide against vaccination.

Dr. Janet Woodcock, the acting commissioner of the F.D.A., said at a news conference that the pause might last only “a matter of days,” although she said that depended on “what we learn in the next few days.” Dr. Schuchat said the pause was enacted partly to “prepare the health care system to recognize and treat patients appropriately.”