The European Medicines Agency safety committee (PRAC) has concluded that a warning about unusual blood clots with low blood platelets should be added to the product information for the COVID-19 Johnson and Johnson vaccine, also known as the Janssen vaccine.

The PRAC concluded that such blood clots should be listed as very rare side effects of the vaccine and that the overall benefits of the vaccine in preventing COVID-19 outweigh the risks of side effects.

In reaching its conclusion, the PRAC 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 the Johnson and Johnson 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.

The PRAC noted that the blood clots occurred mostly at unusual sites such as in veins in the brain and the abdomen 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.

A statement from the EMA said that 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.

The statement said that use of the vaccine during vaccination campaigns at national level will take into account the pandemic situation and vaccine availability in individual EU Member States.

One plausible explanation for the combination of blood clots and low blood platelets put forward by the EMA was an immune response, leading to a condition similar to one seen sometimes in patients treated with heparin, an anticoagulant used to decrease the clotting ability of blood, called heparin induced thrombocytopenia.

The statement emphases the importance of recognising the signs of blood clots and seeking prompt medical attention if such symptoms present.

The EMA said it will continue to monitor the Johnson and Johnson vaccine’s safety and effectiveness and provide the public with the latest information.

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