Benzinga | Apr 7, 2021 11:16AM EDT

Europe's Drug Watchdog Concludes Possible Link Between AstraZeneca COVID-19 Vaccine And Blood Clots

The European Medicines Agency (EMA), after an in-depth analysis, has concluded that unusual blood clots should be listed as a "very rare side effect" of the Oxford/AstraZeneca Plc (NASDAQ: AZN) COVID-19 vaccine.

What Happened: The EMA's safety committee said that it considered all the available evidence around the instances of unusual blood clots with low blood platelets in people who received AstraZeneca's shot. However, the agency confirms that the overall benefit-risk remains positive.

The EMA said most of the blood clot cases reported have occurred in women under 60 years of age within two weeks of their first vaccine dose. However, the specific risk factors have not yet been confirmed.

"A plausible explanation for these rare side events is an immune response to the vaccine similar to one seen in patients treated with heparin," called heparin-induced thrombocytopenia, noted the agency.

The EMA said people who have received this vaccine should "seek medical assistance immediately" if they develop symptoms of this combination of blood clots and low blood platelets.

Why It Matters: In an interview with Italian newspaper Il Messaggero published Tuesday, Marco Cavaleri, chair of the EMA's vaccine evaluation team, said: "In my opinion, we can now say it, it is clear that there is an association with the vaccine. However, we still do not know what causes this reaction."

Last month, EMA said that it had found the AZN shot safe and effective but added if a connection between the clots and the vaccine is established, the EMA will change its recommendations.

Today, Reuters reported that several European countries are looking at a mix of COVID-19 vaccine doses for people who have received the first dose of AstraZeneca shot amid the crisis.

Price Action: AZN shares dropped 0.4% at $49.03 during the market trading hours on the last check Wednesday.