The European Medicines Agency (EMA)’s Pharmacovigilance Risk Assessment Committee (PRAC) has concluded its review of very rare cases of unusual blood clots with low blood platelets (thrombosis in combination with thrombocytopenia) associated with immunisation with the Janssen COVID-19 Vaccine. The PRAC determined that the benefit of the Janssen COVID-19 Vaccine continues to outweigh the potential risks, but that the Summary of Product Characteristics and Package Leaflet should be updated to list these events as very rare side effects of the vaccine.
According to the EMA, the committee considered all available evidence in making this decision, including the eight reports of serious cases of thrombosis in combination with thrombocytopenia from the US, one of which was fatal. As of 13 April 2021, over seven million people had received Janssen’s vaccine in the US.
All the cases occurred in those under 60 years old, within three weeks of vaccination. The majority occurred in women. Based on the current evidence, the committee has not been able to confirm specific risk factors.
PRAC noted that the blood clots predominantly occurred at unusual sites, such as in veins in the brain (cerebral venous sinus thrombosis, CVST), 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 those reported in association with the COVID-19 Vaccine AstraZeneca, now called Vaxzevria. Both Vaxzevria and the Janssen COVID-19 Vaccine are recombinant vector vaccines, using an attenuated virus that cannot cause disease to deliver DNA encoding a portion of the virus to induce an immune response.
The EMA said that healthcare professionals and people who will receive the vaccine should be aware of the possibility of very rare cases of thrombosis in combination with thrombocytopenia occurring within three weeks of vaccination. However, since COVID-19 is associated with a risk of hospitalisation and death, found that the overall benefits of the Janssen COVID-19 Vaccine in preventing the disease outweighs the risks of side effects.
The PRAC did suggest a plausible explanation for thrombosis in combination with thrombocytopenia observed with both Vaxzevria and Janssen COVID-19 Vaccine; it suggested that an immune response to the vaccines could be causing a condition similar to one sometimes observed in patients treated with heparin, called heparin induced thrombocytopenia (HIT).
The committee also emphasised that patients experiencing symptoms of blood clots post vaccination should seek prompt specialist medical treatment and that healthcare professionals should consult applicable guidance and/or consult specialists when treating thrombosis in combination with thrombocytopenia.
The EMA concluded that it will continue to monitor the safety and effectiveness of all vaccines and provide the public with the latest information.
European Janssen COVID-19 Vaccine rollout to resume
Following the PRAC decision, Johnson & Johnson (J&J) has announced that it will resume shipment of the Janssen COVID-19 Vaccine in the European Union (EU), Norway and Iceland.
“The safety and well-being of the people who use our products is our number one priority. We appreciate the rigorous review of the PRAC and share the goal of raising awareness of the signs and symptoms of this very rare event to ensure the correct diagnosis and appropriate treatment,” stated Dr Paul Stoffels, Vice Chairman of the Executive Committee and Chief Scientific Officer at J&J. “We strongly believe in the positive benefits of our single-shot, easily transportable COVID-19 vaccine to help protect the health of people everywhere and reach communities in need globally. We are committed to equitable access and to bringing an affordable COVID-19 vaccine to the public on a not-for-profit basis for emergency pandemic use.”
The US Centers for Disease Control and Prevention (CDC) and Food and Drug Administration (FDA) are currently reviewing the same cases of thrombosis in combination with thrombocytopenia. On the 14 April 2021 the CDC convened a meeting of the Advisory Committee on Immunization Practices (ACIP) to review these cases and assess their potential significance. The ACIP plans to reconvene on the 23 April 2021 for further discussion.
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