(Reuters) -The European Union’s drug regulator on Friday identified a possible link between rare cases of blood clotting in deep veins with Johnson & Johnson (NYSE:)’s COVID-19 vaccine and recommended the condition be listed as a side-effect of the shot.

The European Medicines Agency also recommended that immune thrombocytopenia (ITP), a bleeding disorder caused by the body mistakenly attacking platelets, be added as an adverse reaction with an unknown frequency to the J&J vaccine product information and to AstraZeneca (NASDAQ:)’s vaccine.

J&J did not immediately respond to a request for comment.

Both vaccines were previously associated with the rare combination blood clotting, low platelet counts and thrombocytopenia (TTS)

Both products use harmless vector viruses to instruct the cells of human beings to create a protein which primes their immune systems against further coronavirus attacks.

EMA said the new, possibly life-threatening clotting condition known as venous thromboembolism (VTE) to be included on the J&J product label was separate from TTS.

A clot forms in a vein from a leg, arm, or groin and travels to the lung where it blocks the blood supply.

VTE can be caused by injuries or inability to move for bedridden patients, regardless of vaccines. Risk factors include birth control pills, chronic diseases and certain medications.