COVID-19 vaccine manufacturer Johnson & Johnson has responded to persistent blood clotting rumors, saying that all vaccines prompt a small number of clotting events. According to CNN, while J&J downplayed the number of events and maintained they weren’t proven to be caused by the vaccine, they’re still taking a closer look at the phenomenon.

The European Medicines Agency announced Friday that it would be investigating the allegations.

The announcement noted that there had been four cases where vaccine recipients developed serious blood clots. 

“Our close tracking of side effects has revealed a small number of very rare events following vaccination. At present, no clear causal relationship has been established between these rare events and the Janssen COVID-19 vaccine,” J&J’s Friday statement said.

The drug company said it was “aware” of the issue, but stressed that rare blood clotting had been “reported with all Covid-19 vaccines.” 

Pharmaceutical giant Johnson & Johnson said it had identified a batch of doses at a plant in Baltimore run by Emergent BioSolutions "that did not meet quality standards" but did not confirm the specific number affected Pharmaceutical giant Johnson & Johnson said it had identified a batch of doses at a plant in Baltimore run by Emergent BioSolutions "that did not meet quality standards" but did not confirm the specific number affected Photo: AFP / JUSTIN TALLIS

J&J is hoping that their single-shot vaccine will help to revitalize a public image somewhat marred by perceived drug profiteering and a series of lawsuits over talcum powder linked to cancer. It was also implicated in the opioid crisis, running ads for painkillers as addiction ravaged the nation. 

The J&J vaccine was the third approved for emergency use in the U.S., where officials hoped it would speed a vaccination effort hampered by Trump-era delays.

It most recently made headlines for less encouraging reasons: a Colorado plant ruined 15 million doses during the manufacturing process, although the botched batch was caught before getting near distribution stages. 

Johnson & Johnson’s vaccine has a number of practical advantages over those made by Moderna and Pfizer: its single-dose regimen does not require refrigeration, making for easy transport and storage.

While experts look into unintended side effects, they’re telling anyone who gets the vaccine to be on the lookout for early warning signs of more severe complications: shortness of breath, chest pain, swelling in the leg, persistent belly pain, neurological symptoms, excessive or easy bruising, or tiny blood spots under the skin past the injection site.