There is a "possible link" between Johnson & Johnson's single-dose vaccine and very rare cases of blood clots, the European Medicines Agency (EMA) told reporters on Tuesday, emphasising that the benefits of the vaccine continue to outweigh the risks.
EMA's safety committee said that the serious blood clots should be listed as "very rare side effects" of the vaccine, the agency said in a statement earlier on Tuesday.
The EU medicines regulator had reviewed eight reports from the United States of "serious cases of unusual blood clots associated with low levels of blood platelets", one of which was fatal.
No cases were reported in the European Union, said EMA chief Emer Cooke.
The vaccine was authorised in March for use in the bloc "but has not yet been broadly rolled out", noted Sabine Straus, chairperson of EMA's evaluation committee of risks and pharmacovigilance (PRAC).
More than seven million people in the US have received the Johnson & Johnson vaccine. The US Centres for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA) announced a pause to vaccination last week over the blood clot reports.
Majority of young women
All of the rare cases of blood clotting happened in people under the age of 60 within the first three weeks following vaccination; the majority of them were women and the median age was 33, EMA officials told reporters.
Healthcare workers and those who have received the vaccine should be aware of potential symptoms of these rare blood clots. They include shortness of breath, chest pain, leg swelling, abdominal pain, headache, blurred vision or tiny blood spots under the skin.
The early intervention of a specialist can change the outcome for the patient, Cooke said.
"The reported combination of blood clots and low blood platelets is very rare, and the overall benefits of COVID-19 Vaccine Janssen (Johnson & Johnson) in preventing COVID-19 outweigh the risks of side effects," the EU medicines regulator insisted.
'Similarities' with AstraZeneca
The cases reported with Johnson & Johnson's vaccine were similar to the rare blood clot cases linked to the AstraZeneca vaccine, EMA said. Both vaccines used an adenovirus vector.
However, Straus noted there were differences between both the vaccines since Johnson & Johnson's uses a human adenovirus while AstraZeneca is chimpanzee-based. Both vaccines also use a different spike protein, she said.
Considering that the Sputnik-V vaccine also uses an adenovirus vector, the EU regulator will "pay close attention" to the issue of rare blood clots as it reviews the jab.
According to the latest available data, a total of 287 cases of unusual blood clots were reported following the AstraZeneca vaccine, 25 with the Pfizer-BioNTech vaccine and 5 with Moderna, EMA told reporters.
Multiple EU countries have issued suspensions or age limits on the AstraZeneca coronavirus vaccine amid a possible link to blood clots.
Science analytics company Airfinity told Euronews earlier this week that suspending both the AstraZeneca and Johnson & Johnson vaccine in the EU could delay the bloc's goal to inoculate 70% of the adult population by the end of the summer.
European Commission President Ursula von der Leyen welcomed "the announcement on the safety of the Johnson & Johnson vaccine."
"This is good news for the roll-out of vaccination campaigns across the EU," she tweeted.
"Our investigations will continue. We will be imposing studies on Janssen to look further into the data. EMA has also commissioned research into the cases of thrombosis in COVID-19 disease through two research consortiums," Cooke told reporters.