Twelve of the 15 women in the confirmed cases developed blood clots in the brain. Many had blood clots elsewhere as well. Initial symptoms, which include a headache, usually begin six or more days after vaccination, said Dr. Shimabukuro. As the disorder develops, it can cause increased headaches, nausea and vomiting, abdominal pain, weakness in one side of the body, difficulty speaking, loss of consciousness, and seizures.
Dr. Shimabukuro found 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 could increase the risk of developing a coagulation disorder after vaccination.
Patients’ symptoms closely resemble a rare syndrome that can be caused by heparin, a widely used blood thinner, said Dr. Michael Streiff, a hematologist at Johns Hopkins University, joined the panel. Heparin, which could typically be used to treat blood clots, shouldn’t be used to treat these patients, he said.
Doctors should consider the rare coagulation disorder in patients who have blood clots and low platelet counts within three weeks of receiving the Johnson & Johnson vaccine, said Dr. Streiff.
“Knowing that this syndrome exists will help improve outcomes,” he said.
The committee could recommend Johnson & Johnson put up a formal warning label about the side effects, as the company has done in the European Union. About 10 million doses or more of the vaccine, which is manufactured at the company’s facility in the Netherlands, are on shelves in the United States and could be used immediately.
The meeting comes as the federal government is also investigating issues at a Baltimore factory that is slated to meet the country’s demand. Emergent BioSolutions, the operator of the facility, has manufactured tens of millions of doses of Johnson & Johnson’s vaccine, but they cannot be distributed until regulatory agencies certify the facility.
After Emergent had to discard up to 15 million potentially contaminated doses of the vaccine last month, federal regulators conducted an inspection that found a number of problems, including the risk of other lots being contaminated.
