The European Union’s pharmaceuticals regulator detected a possible relationship between Johnson & Johnson’s COVID-19 vaccine and rare incidents of blood clotting in deep veins on Friday. It recommended that the condition is mentioned as a side effect of the shot, Reuters reported.

Immune thrombocytopenia (ITP), a bleeding disorder caused by the body erroneously attacking platelets, should be added as an adverse response with an unknown frequency to the J&J vaccination product information and AstraZeneca’s vaccine, according to the European Medicines Agency.

While the chances of these conditions occurring are low, J&J said the product information would be updated as it continues to work closely with authorities, including the European Medicines Agency (EMA).

“We strongly support raising awareness of the signs and symptoms of rare events to ensure they can be quickly identified and effectively treated,” the company said.

Both the J&J and AstraZeneca vaccines have previously been linked to thrombosis with thrombocytopenia syndrome, a rare combination of blood clotting and low platelet counts (TTS).

The two products are based on virus vectors that instruct human cells to produce a protein that prepares the immune system for future coronavirus infections.

The EMA stated that venous thromboembolism (VTE), a new potentially life-threatening clotting condition to be included on the J&J product label, was distinct from TTS.

VTE usually starts with a clot forming in a vein in the leg, arm, or groin, which then travels to the lungs and blocks blood flow.

VTE is most commonly caused by injury or lack of movement in bedridden patients, regardless of vaccine use. Birth control pills, as well as a number of chronic illnesses, are considered risk factors.

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