On 20 April 2021, the Pharmacovigilance Risk Assessment Committee (PRAC) at the European Medicines Agency (EMA) decided that the occurrence of unusual blood clots with a reduced platelet count should be included in the Summary of Product Characteristics (SPC) and the package leaflet for the COVID-19 vaccine Janssen as very rare adverse effect. For this reassessment, the PRAC evaluated all data available – including eight case reports of serious unusual blood clots in connection with low platelet levels from the USA. One person died. Up to that time, more than seven million persons in the USA had been vaccinated with COVID-19 vaccine Janssen.
The PRAC has pointed out that the rare observed thromboses (with thrombocytopenia) occurred in unusual sites including sinus veins (sinus vein thromboses), and intestinal veins (splanchnicus veins). They also included arterial thromboses, which occurred together with low platelet levels, and occasionally bleeding. The cases reported up to now refer to persons under 60 years of age, predominantly women, within three weeks after administration of the first dose. The cases studied were very similar to those which occurred after the administration of the vaccine Vaxzevria by AstraZeneca.
The PRAC has also pointed out that the COVID-19 disease itself is related to a risk of serious courses with hospitalisation and death. The reported combination of blood clots and reduced platelet count is very rare, and the overall benefit of the vaccine in preventing COVID-19 outweighs the risk involved in its adverse effects.
Updated: 23.04.2021
