The United States can immediately resume use of Johnson & Johnson's COVID-19 vaccine, top health regulators said on Friday.
It comes following a 10-day pause to investigate the vaccine's link to extremely rare but potentially deadly blood clots.
The Centers for Disease Control and Prevention (CDC) and Food and Drug Administration said the risks of experiencing the syndrome involving severe blood clots and low platelets as a result of the vaccine was very low. They found 15 cases in the 8 million shots given.
"We are no longer recommending a pause in the use of this vaccine," CDC Director Rochelle Walensky told a news briefing. "Based on the in-depth analysis, there is likely an association but the risk is very low."
Top US FDA officials said the decision was effective immediately, clearing the way for shots in arms as early as Saturday. The agency said it would warn of the risk in an updated fact sheet given to vaccine recipients and providers.
The agencies made the decision following a meeting of outside advisers to the CDC who recommended that the vaccine pause be ended.
In an analysis presented at the meeting, CDC staff said that the cases of the syndrome that they had found occurred at a rate of seven per one million doses in women under age 50, with the highest risk occurring among women aged 30 to 39.
For women over age 50 and for all men, the clots appeared at a rate of one per one million doses, the analysis showed. In all, there were three deaths, officials said.
After a day-long meeting, the CDC panel voted 10-4 that the J&J vaccine be used as recommended in people 18 years of age and older, the parameters of its current FDA authorisation.
Dr. Jesse Goodman, an infectious disease expert at Georgetown University in Washington and a former chief scientist at the FDA, said the risk was not trivial, but still small.
"But we should keep it in perspective. I mean the risk of dying from a car accident in your life is something like one in 100, the risk of being struck by lightning is something like one in 15,000," Goodman said.
Unlike the highly effective vaccines by Pfizer Inc and Moderna Inc, which require two doses and must be kept frozen at ultra-cold temperatures, J&J's vaccine can be given in a single dose and stored at regular refrigeration temperatures, making it a better option for hard-to-reach areas.
Johnson & Johnson shares closed up 0.2% at $165.52.
The US decision follows a similar one by the European Medicines Agency, which on Tuesday said the benefits of the J&J shot outweighed its risks and recommended adding a warning about unusual blood clots with low blood platelet counts to the vaccine's product label.