The six reported cases were among more than 6.8 million doses of the Johnson & Johnson vaccine administered in the United States.
All six cases occurred among women between the ages of 18 and 48, and symptoms occurred 6 to 13 days after vaccination, according to a joint statement on Tuesday from Dr. Anne Schuchat, principal deputy director of the CDC and Dr. Peter Marks, director of the FDA’s Center for Biologics Evaluation and Research.
“CDC will convene a meeting of the Advisory Committee on Immunization Practices (ACIP) on Wednesday to further review these cases and assess their potential significance,” the statement said. “FDA will review that analysis as it also investigates these cases. Until that process is complete, we are recommending a pause in the use of this vaccine out of an abundance of caution.”
Johnson & Johnson issued a statement on Tuesday noting that the company has decided to “proactively delay the rollout” of its vaccine in Europe.
For people who have received the Johnson & Johnson shot, those who have developed severe headache, abdominal pain, leg pain or shortness of breath within three weeks after vaccination should contact their health care provider, according to the statement.
The statement also noted that these adverse events “appear to be extremely rare.”
The Johnson & Johnson vaccine is an adenovirus vector vaccine — the same type as AstraZeneca’s coronavirus vaccine.
Dr. Carlos del Rio, executive associate dean of the Emory University School of Medicine said “the adenovirus vector vaccine may have something to do with it,” del Rio said. The two other Covid-19 vaccines authorized for emergency use in the United States — Pfizer’s and Moderna’s — are mRNA vaccines, which are a different type.
The new announcement from the FDA and CDC means all federal health channels — mass vaccination sites, community health centers and the like — that were previously administering the Johnson & Johnson vaccine will immediately stop for the time being, according to a federal health official.