Eight cases of serious, unusual blood clots associated with low levels of blood platelets, one of which was fatal, have been seen in the U.S. after administration of Johnson & Johnson COVID-19 vaccine. On April 20, European Medicines Agency’s safety committee (PRAC) based on these cases “concluded that a warning about unusual blood clots with low blood platelets should be added to the product information for COVID-19 Vaccine Janssen”. The safety committee also “concluded that these events should be listed as very rare side effects of the vaccine”. As of 13 April 2021, over seven million people had received the vaccine in the U.S.
In a press release, the EMA said that it found “ possible link to very rare cases of unusual blood clots with low blood platelets” following administration of Johnson and Johnson vaccine.
On April 13, the U.S. called for a pause in Johnson & Johnson vaccine use when six cases of a rare blood-clotting disorder were seen in the vaccinated people.
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All the eight cases were seen in those under 60 years of age within three weeks after vaccination, the majority being in women. “Based on the currently available evidence, specific risk factors have not been confirmed,” the EMA said in a release.
Kai Kupferschmidt, a science journalist, tweeted saying that Sabine Straus, Chair of EMA, told the press that though the U.S. paused vaccination on April 13, cases can still occur for three weeks after immunisation. “So we still have to wait and see if there are more cases coming in, so it's too early to say anything about the real occurrence of the cases,” Ms. Straus had apparently warned.
“At this moment, it's not possible to identify clear risk factors for the occurrence of these very rare events, such as gender or age”, Ms. Straus told the press.
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The safety committee also 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 had close similarity to cases seen after administration of AstraZeneca vaccine.
The EMA stressed that the reported “combination of blood clots and low blood platelets is very rare, and the overall benefits of COVID-19 Vaccine Janssen [owned by Johnson and Johnson] in preventing COVID-19 outweigh the risks of side effects”.
The EMA listed out the symptoms to look out for within three weeks after vaccination. These include shortness of breath; chest pain; swelling in the leg; persistent abdominal pain; neurological symptoms, including severe or persistent headaches or blurred vision; and skin bruising beyond the site of injection.
The safety committee emphasised the importance of prompt specialist medical treatment. “By recognising the signs of blood clots and low blood platelets and treating them early, healthcare professionals can help those affected in their recovery and avoid complications,” the committee said.