» CDC holds emergency meeting as J&J doses remain in limbo,

Clot concerns could hurt public confidence in the one-shot vaccine.

Johnson & Johnson’s COVID19 vaccine will remain in limbo a while longer after U.S. health advisers told the government 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 potential 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 vaccine alternatives to do without the J&J vaccine for a time, but other countries anxiously awaiting the one-and-done shot may not.

One committee member, Dr. Grace Lee, was among those who advocated tabling a vote. She echoed concerns about getting more data to better understand the size of the risk and whether it was greater for any particular group of people.

“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 Lee, of Stanford University.

The clots under investigation are highly unusual. They occurred in strange places, in veins that drain blood from the brain, and in people with abnormally low levels of clot-forming platelets. The six casesraised 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 clot concerns could undermine public confidence in a vaccine many hoped would help some of the hardest-to-reach populations — in poor countries or in places like homeless shelters in the U.S.