One US patient died from blood clotting complications after receiving the Johnson & Johnson Covid vaccine while another is in critical condition, a senior scientist for the Food and Drug Administration said Tuesday.

Overall, six women aged between 18 to 48 developed a rare form of brain blood clotting with low blood platelets between six and 13 days after receiving the shot.

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“One case was fatal, and one patient is in critical condition,” Peter Marks said in a call with reporters. 

Marks drew a link with a similar disorder seen in Europe after people received the AstraZeneca vaccine, which is also based on adenovirus vector technology.

The illness is thought to derive from a rare immune response to the vaccines that triggers the activation of clots.

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Anne Schuchat, a senior official with the Centers for Disease Control and Prevention, added that the risk was very low for people who had received the vaccine a month or more ago. 

“For people who recently got the vaccine within the last couple of weeks, they should be aware to look for any symptoms. 

“If you’ve received a vaccine and develop severe headaches, abdominal pain, leg pain, or shortness of breath, you should contact your health care provider,” she added.