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EMA: “Blood clots should be listed as rare Johnson & Johnson vaccine side effect”

The European Medicines Agency (EMA) said on Tuesday that “blood clots should be listed as a ‘very rare’ side effect of Johnson & Johnson vaccine, but benefits still outweigh risks.

According to a statement released on Tuesday afternoon, EMA’s safety committee recommends that a warning of “very rare cases of unusual blood clots with low blood platelets” should be added to the list of side effects for the Janssen vaccine.

EMA confirms overall benefit-risk remains positive

At its meeting of 20 April 2021, EMA’s safety committee (PRAC) concluded that a warning about unusual blood clots with low blood platelets should be added to the product information for COVID-19 Vaccine Janssen. PRAC also concluded that these events should be listed as very rare side effects of the vaccine.

In reaching its conclusion, the Committee took into consideration all currently available evidence including eight reports from the United States of serious cases of unusual blood clots associated with low levels of blood platelets, one of which had a fatal outcome. As of 13 April 2021, over 7 million people had received Janssen’s vaccine in the United States.

All cases occurred in people under 60 years of age within three weeks after vaccination, the majority in women. Based on the currently available evidence, specific risk factors have not been confirmed.

PRAC noted that the blood clots occurred mostly at unusual sites such as in veins in the brain (cerebral venous sinus thrombosis, CVST) and the abdomen (splanchnic vein thrombosis) and in arteries, together with low levels of blood platelets and sometimes bleeding. The cases reviewed were very similar to the cases that occurred with the COVID-19 vaccine developed by AstraZeneca, Vaxzevria.

Healthcare professionals and people who will receive the vaccine should be aware of the possibility of very rare cases of blood clots combined with low levels of blood platelets occurring within three weeks of vaccination.

COVID-19 is associated with a risk of hospitalisation and death. The reported combination of blood clots and low blood platelets is very rare, and the overall benefits of COVID-19 Vaccine Janssen in preventing COVID-19 outweigh the risks of side effects.

EMA’s scientific assessment underpins the safe and effective use of COVID-19 vaccines. Use of the vaccine during vaccination campaigns at national level will take into account the pandemic situation and vaccine availability in individual Member States.

One plausible explanation for the combination of blood clots and low blood platelets is an immune response, leading to a condition similar to one seen sometimes in patients treated with heparin called heparin induced thrombocytopenia, HIT.

PRAC emphasises the importance of prompt specialist medical treatment. By recognising the signs of bloods clots and low blood platelets and treating them early, healthcare professionals can help those affected in their recovery and avoid complications. Thrombosis in combination with thrombocytopenia requires specialised clinical management. Healthcare professionals should consult applicable guidance and/or consult specialists (e.g., haematologists, specialists in coagulation) to diagnose and treat this condition.

As for all vaccines, EMA will continue to monitor the vaccine’s safety and effectiveness and provide the public with the latest information.

A similar signal evaluation was recently finalised for another COVID-19 vaccine, Vaxzevria (previously COVID-19 Vaccine AstraZeneca).

Information for the public

  • Cases of unusual blood clots with low platelets have occurred in people who received Janssen’s COVID-19 vaccine in the United States.
  • The risk of having this side effect is very low, but people who will receive the vaccine should still be aware of symptoms so they can get prompt medical treatment to help recovery and avoid complications.
  • Individuals must seek urgent medical attention if they have any of the following symptoms in the three weeks after being vaccinated with COVID-19 Vaccine Janssen:
    • shortness of breath
    • chest pain
    • leg swelling
    • persistent abdominal (belly) pain
    • neurological symptoms, such as severe and persistent headaches or blurred vision
    • tiny blood spots under the skin beyond the site of the injection.
  • Speak to your healthcare professional or contact your relevant national health authorities if you have any questions about your vaccination.

The EMA press release HERE includes also information for healthcare professionals.


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  1. We have lost a few weeks of giving jabs trying to get back to normal. Even a dude like me could calculate that the risk 1 to a million is smaller as getting Covid and getting seriously ill or even die.