Johnson & Johnson’s Covid-19 vaccine will remain in limbo a while longer after US 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 7m US inoculations with the one-dose vaccine. But the government recommended a pause in Johnson & Johnson 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 US.
At an emergency meeting, advisers to the Centers for Disease Control and Prevention wrestled with the fact that the US has enough vaccine alternatives to do without the Johnson & Johnson 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 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 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 US.
Health officials recommended the Johnson & Johnson timeout in part to make sure doctors know how to recognize and treat the unusual condition.
The US set up intensive systems to track the safety of Covid-19 vaccines, knowing that side effects too rare to have occurred in studies of thousands of people could pop up once millions rolled up their sleeves. Shimabukuro said spotting such a rare potential risk amid the nation’s huge vaccine rollout “is an example of a success story for vaccine safety”.
The setback for Johnson & Johnson comes as the worldwide death toll from Covid-19 approaches 3 million, including more than 560,000 in the US, which continues to report tens of thousands of new infections every day and an average of almost 1,000 deaths.
So far, the Johnson & Johnson vaccine has been a minor player in US vaccinations. More than 122 million Americans have received at least one vaccine dose, the vast majority with shots made by Moderna or Pfizer, and nearly 23% are fully vaccinated.
Both companies are on track to have delivered 300m doses each by mid- to late July – and federal health authorities stress that there are no signs of the unusual clots with the Moderna and Pfizer vaccines.
Vaccinations are slower in Europe, where many countries have struggled for supply. Johnson & Johnson delayed some of its European deliveries amid the clot evaluation, but Poland said it would use the batch it already has in hand. European medical regulators plan to issue their own evaluation of the clot issue next week.
Health officials caution against confusing the normal flu-like symptoms that occur a day or two after many Covid-19 vaccination with the clot concern. The problematic clot symptoms, such as severe headache or severe abdominal pain, have occurred about a week to three weeks after the Johnson & Johnson shot.