Young people under the age of 30 in the UK are to be offered an alternative to the Oxford/AstraZeneca vaccine as evidence emerges of a link between the jab and extremely rare blood clots that have been detected in some recipients.
A review by the European Medicines Agency has also concluded that these clots “should be listed as very rare side effects” of the vaccine.
The condition generating alarm is called cerebral venous sinus thrombosis (CVST), when blood clots in the veins that run from the brain, sometimes culminating in death.
In the cases of concern, which appear to be more prevalent in women under 60, this has been combined with thrombocytopenia, where a patient also presents abnormally low levels of platelets.
Clotting in the abdomen (splanchnic vein thrombosis) has also been detected among some recipients of the vaccine, according to the EMA.
Dr June Raine, chief of the UK’s Medicines and Healthcare products Regulatory Agency (MHRA), said its safety monitoring systems were detecting "a potential side effect of the Covid-19 vaccine AstraZeneca in an extremely small number of people".
"The evidence is firming up and our review has concluded that, while it's a strong possibility, more work is needed to establish beyond all doubt that the vaccine has caused these side effects," she said.
The MHRA said there had been 79 cases of CVST associated with low platelet cells in the blood. These conditions emerged after administration of the first dose.
Nineteen people have died as a result of the clotting disorders, three of whom were aged under 30, the MHRA added.
Dr Raine said anyone who has symptoms four days after vaccination should come forward for swift medical advice.
Symptoms include, she added, a new onset of a severe or persistent headache or blurred vision, shortness of breath, chest pain, leg swelling, persistent abdominal pain, unusual skin bruising, or pin-point spots beyond the injection site.
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