"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," the EMA said in a statement, referring to Johnson & Johnson’s European subsidiary. "PRAC also concluded that these events should be listed as very rare side effects of the vaccine."
At the same time, the regulator added that blood clots with low platelets are a rare side effect of the vaccine and its overall benefits outweigh the risks.
"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," the EMA said.
EMA Executive Director Emer Cooke stressed the importance of the drug review as many EU countries rely on its conclusions to continue with the rollout.
"I must stress that we have seen no cases in the EU, but in fact, there has been very little rollout and a lot of countries are waiting for the outcome of this review to ensure that we have the right information about the product to allow it to be rolled out safely," he stated.
Concerning the comparisons between the Johnson & Johnson and AstraZeneca drugs, PRAC chair Sabine Straus noted that though the two vaccines may share similarities, the differences in their composition should not be ignored.
"Indeed, we have seen that the AstraZeneca vaccine is an adenovirus-based vaccine, just as the Janssen vaccine, so there are some similarities between the two vaccines, but there are also differences. For example, the AstraZeneca is a chimpanzee-based adenovirus, and the Janssen is a human adenovirus, and also there are differences between the spike protein between Janssen and AstraZeneca," she said.
According to Straus, it is too early to reach any conclusions and more research into the hypotheses to explain the phenomenon is required.