On Tuesday, acting Food and Drug Administration chief Dr. Janet Woodcock announced that the agency, together with the Centers for Disease Control, would recommend a temporary pause on the use of the Johnson & Johnson coronavirus vaccine, citing rare but severe brain blood clots in six individuals out of the 7.5 million Americans who received the shot. While she anticipated that the delay would only last for a few days, a CDC advisory board said Wednesday that they wanted more data before making a decision on how to move forward with the J&J vaccine candidate. The Advisory Committee on Immunization Practices will now reconvene in a week to ten days, as they consider reports on the clotting and determine whether to recommend the continued use of the shot.
The CDC advisory committee has reviewed details from the six patients, all women between the ages of 18 and 48. Each patient developed the clots within one to three weeks of vaccination; one Virginia woman died, another patient in Nebraska is in critical condition, three more remain in the hospital, and two have been discharged.
At the meeting on Wednesday, a CDC official and a Johnson & Johnson executive added that all of the women were white, and only one was taking hormonal contraceptives, which can potentially cause blood clots. Aran Maree, the chief medical officer for the division of Johnson & Johnson that developed the vaccine, revealed that two additional clotting cases occurred during a clinical trial for the vaccine. Tom Shimabukuro, the head of the CDC’s vaccine safety team, added that the clots were concerning because they were associated with low levels of blood cells involved in clotting, which is abnormal in healthy individuals. “We have a picture where we have clots forming in large [blood] vessels in the presence of low platelets, so it’s kind of a paradox here,” Shimabukuro said. “This is unusual — it usually doesn’t happen.” As the Washington Post notes, that combination “has also been seen, rarely, among people who received [the] vaccine developed by AstraZeneca and University of Oxford.” Several European nations have stopped the rollout of the AstraZeneca candidate due to similar concerns about rare blood clots.
When the panel reconvenes in late April, they could vote to extend the total pause on J&J shots, recommend the vaccine be given only to specific groups, or recommend the vaccine for all adults over 18. The recommendation on Tuesday to pause vaccinations came in part from worries that clinicians did not know how to detect or treat the blood clots, and that clotting from the J&J vaccine should not be treated with heparin, a common anticoagulant that should be avoided because they could make the clots worse.