UPDATE: J&J Vaccine to Remain in Limbo While Officials Seek Evidence

Johnson & Johnson's COVID-19 vaccine will remain in limbo for a while longer after government health advisers declared Wednesday that they need more evidence to decide if a handful of unusual blood clots were linked to the shot — and if so, how big the risk really is.

The reports are exceedingly rare — six cases out of more than 7 million U.S. inoculations with the one-dose vaccine. But the government recommended a pause in J&J vaccinations this week, not long after European regulators declared that such clots are a rare but possible risk with the AstraZeneca vaccine, a shot made in a similar way but not yet approved for use in the U.S.

At an emergency meeting, advisers to the Centers for Disease Control and Prevention wrestled with the fact that the U.S. has enough alternative shots to vaccinate its population but other countries anxiously awaiting the one-and-done vaccine may not.

“I continue to feel like we’re in a race against time and the variants, but we need to (move forward) in the safest possible way,” said CDC adviser Dr. Grace Lee of Stanford University, who was among those seeking to postpone a vote on the vaccine.

Authorities have studied the clots for only a few days and have little information to judge the shot, agreed fellow adviser Dr. Beth Bell of the University of Washington.

“I don’t want to send the message there is something fundamentally wrong with this vaccine,” Bell said. “It’s a very rare event. Nothing in life is risk-free. But I want to be able to understand and defend the decision I’ve made based on a reasonable amount of data."

These are not run-of-the-mill blood clots. They occurred in unusual places, in veins that drain blood from the brain, and in people with abnormally low levels of clot-forming platelets. The six cases raised an alarm bell because that number is at least three times more than experts would have expected to see even of more typical brain-drainage clots, said CDC's Dr. Tom Shimabukuro.

“What we have here is a picture of clots forming in large vessels where we have low platelets,” Shimabukuro explained. “This usually doesn’t happen,” but it’s similar to European reports with the AstraZeneca vaccine.

The good news: The government says there are no signs of similar clots after vaccination with the Pfizer and Moderna shots that are the mainstay of the COVID-19 fight in the U.S.

The J&J cases now under investigation are all among women younger than 50. But the advisory panel stressed that there's not enough information to tell if only certain groups would be at risk. In Europe, most but not all cases following AstraZeneca vaccinations have been among women under 60, leading different countries to use that vaccine in varying ways.