The European Union’s drug regulator has started a review to assess blood clots in people who received Johnson & Johnson’s Covid-19 vaccine.
Four serious cases of unusual clots accompanied by low blood platelets, one of which was fatal, have been reported after immunisation with the Johnson & Johnson shot, the European Medicines Agency said on Friday.
The regulator is now scrutinising potential safety issues for two Covid vaccines after it linked AstraZeneca's shot to rare blood clots on Wednesday.
Johnson & Johnson is working with regulators to assess data and "at present, no clear causal relationship has been established" with the vaccine, the company said.
The potential nexus was enough to spook investors, however, with shares on Friday trading as much as 1.6 per cent lower.
One of the cases following Johnson & Johnson vaccination happened during a clinical trial. At the time, the company said it had found no evidence the vaccine was at fault.
Three others occurred in the US where the shot has been given to almost 5 million people.
While Johnson & Johnson’s vaccine is approved in the EU, its distribution isn’t expected to start until later this month.
The under-fire bloc is relying on the one-shot vaccine to boost its spluttering immunisation drive, especially after several member states imposed restrictions on AstraZeneca's shot.
The EU regulator also started a review to assess five reported cases of a rare disorder called capillary leak syndrome in people who received the AstraZeneca vaccine.
It said it was unclear whether the vaccine was linked to the disorder, in which fluid leaking from blood vessels causes tissue to swell and blood pressure to drop.
Separately, the EU regulator said it doesn't yet have enough evidence to approve the Russian Sputnik V vaccine.
The Johnson & Johnson, AstraZeneca and Sputnik shots all use an adenovirus – the cause of some common colds – to deliver the coronavirus antigen and generate an immune response.
If this is the reason for the rare side effects observed with the AstraZeneca vaccine, shots from Johnson & Johnson, Sputnik and Chinese drugmaker CanSino Biologics would also be at risk, said Bloomberg analyst Sam Fazeli.
