Roughly 10 million doses or more of the Johnson & Johnson vaccine, produced at the company’s factory in the Netherlands, are sitting on shelves across the United States and could be deployed immediately. Several states, including Texas, Alabama, Utah and Wisconsin, said they expected to follow the recommendations of the C.D.C. and F.D.A. once the decision was made.
The vaccine has immense potential benefits. If vaccinations resume for all adults, 26 to 45 cases of the clotting disorder would be expected over the next six months, according to a model that Dr. Sara Oliver, a C.D.C. scientist, presented at Friday’s meeting. However, 600 to 1,400 fewer Covid-19 related deaths would be expected over the same time period.
The vaccine, which is easy to store and requires just one shot, is also especially well-suited for use in hard-to-reach populations, including people who are homebound, homeless, or incarcerated.
Additional potential cases of the clotting disorder, including some in men, are currently being reviewed. Dr. Shimabukuro also mentioned one case that developed in a 25-year-old man who participated in a clinical trial of the vaccine.
Twelve of the 15 women in the confirmed cases developed blood clots in the brain. Many also had clots elsewhere. Initial symptoms, which include headaches, typically begin six or more days after vaccination, Dr. Shimabukuro said. As the disorder develops, it can cause more severe headaches, nausea and vomiting, abdominal pain, weakness on one side of the body, speech difficulties, loss of consciousness and seizures.
Dr. Shimabukuro noted that seven of the women were obese, two had hypothyroidism, two had high blood pressure, and two were using oral contraceptives. It is not yet clear whether any of these factors might increase the risk of developing the clotting disorder after vaccination.
The patients’ symptoms closely resemble a rare syndrome that can be caused by heparin, a widely used blood thinner, Dr. Michael Streiff, a hematologist at Johns Hopkins University, told the panel. Heparin, which might typically be used to treat blood clots, should not be used to treat these patients, he said.