More than 6.8 million doses of the J&J vaccine have been administered in the U.S., the vast majority with no or mild side effects.
WASHINGTON — The U.S. on Tuesday recommended a “pause” in using the single-dose Johnson & Johnson COVID-19 vaccine to investigate reports of rare but potentially dangerous blood clots, a development that could jeopardize the rollout of vaccines around the world.
The Centers for Disease Control and Prevention and the Food and Drug Administration announced that they were investigating unusual clots that occurred 6 to 13 days after vaccination. The FDA commissioner said she expected the pause to last a matter of days.
The clots occurred in veins that drain blood from the brain and occurred together with low platelets, the fragments in blood that normally form clots. All six cases were in women between the ages of 18 and 48. One person died, and all of the cases remain under investigation.
More than 6.8 million doses of the J&J vaccine have been given in the U.S., the vast majority with no or mild side effects.
Any slowdown in the dissemination of the shots could have broad implications for the global vaccination effort. The J&J vaccine held particular promise for less affluent countries because its single-dose regimen and relatively simple storage requirements would make it easier to use in the developing world.
The FDA said the cases under investigation appear similar to unusual clots that European authorities say are possibly linked to another COVID-19 vaccine not yet cleared in the U.S., from AstraZeneca. European regulators have stressed that the AstraZeneca risk appears to be lower than the possibility of developing clots from birth control pills.
Federally run mass vaccination sites will pause the use of the J&J shot, and states and other providers are expected to follow. The other two authorized vaccines, from Moderna and Pfizer, make up the vast share of COVID-19 shots administered in the U.S. and are not affected by the pause.
“I’d like to stress these events appear to be extremely rare. However COVID-19 vaccine safety is a top priority,” FDA Acting Commissioner Janet Woodcock said at a news conference. “We expect it to be a matter of days for this pause.”
