Johnson & Johnson is delaying the rollout of its single-dose vaccine in Europe because of concerns over very rare blood clots.
It comes just days before it was due to start being rolled out across the EU.
Earlier today the regulator in the US recommended a “pause” in the vaccine's deployment there.
The decision was in response to six cases of blood clotting identified among the nearly seven million people who'd received it.
Officials said such cases appeared to be extremely rare, but they were recommending the pause out of an abundance of caution while they investigate the cases.
Today FDA and @CDCgov issued a statement regarding the Johnson & Johnson #COVID19 vaccine. We are recommending a pause in the use of this vaccine out of an abundance of caution.
— U.S. FDA (@US_FDA) April 13, 2021
In a statement, Johnson & Johnson said: "We are aware of an extremely rare disorder involving people with blood clots in combination with low platelets in a small number of individuals who have received our COVID-19 vaccine.
"The United States Centers for Disease Control (CDC) and Food and Drug Administration (FDA) are reviewing data involving six reported US cases out of more than 6.8 million doses administered. Out of an abundance of caution, the CDC and FDA have recommended a pause in the use of our vaccine.
"In addition, we have been reviewing these cases with European health authorities. We have made the decision to proactively delay the rollout of our vaccine in Europe."
They added that they 'strongly support' open communication of the information to healthcare professionals and the public.
It comes just a day after officials in Ireland recommended against using the AstraZeneca vaccine in people aged under 60, amid concerns over blood clots as a potential very rare side effect of the vaccine.
