European Union medical regulators said Wednesday that there is a possible link between the AstraZeneca coronavirus vaccine and isolated cases of blood clotting in some adults who'd received the shot.
The EU's European Medicines Agency concluded after studies that blood clotting could be listed as a possible side effect from AstraZeneca's Vaxzevria COVID-19 vaccine. The EMA's safety committee said, however, that it might occur only in "very rare" cases.
"A plausible explanation for these rare side events is an immune response to the vaccine similar to one seen in patients treated with heparin," EMA Executive Director Emer Cooke told reporters, according to CNBC.
The EMA reviewed 62 cases of blood clotting in the brain, of which 18 were fatal. The cases were found in areas where about 25 million people received the AstraZeneca vaccine.
AstraZeneca has previously said studies have found no higher risk of blood clots as a result of its vaccine.
The EMA said it's commissioned more research to investigate the link. The regulator said health professionals and recipients of the vaccine should watch for possible symptoms in the first two weeks, which include shortness of breath, chest pain, leg swelling, abdominal pain, headaches and blurred vision.
Several European countries briefly suspended their use of the vaccine, developed by AstraZeneca and Britain's University of Oxford, last month due to the reported clotting cases. Most have since resumed its use.
German officials last week recommended that people under 60 who have received the first shot get their booster dose with a different vaccine.
The World Health Organization, Britain's medicines regulator and the International Society on Thrombosis and Hemostasis have all said that the benefits of the AstraZeneca shot far outweigh the risks.