Reports of an unusual form of blood clot in the head, known as sinus vein thrombosis, prompted several European countries to temporarily halt the use of the AstraZeneca vaccine earlier this month.
Canada and Germany have suspended the use of the Oxford-AstraZeneca Covid vaccine for younger people over concerns it may be linked to rare blood clots.
Canada’s National Advisory Committee on Immunisation (NACI), which provides guidance on vaccines in the county, has recommended the jab not be used in people under the age of 55 while the issue was investigated.
Meanwhile, Germany’s medical regulator paused the vaccine rollout in people under 60 after it announced 31 cases of rare blood clots in people who had recently received the jab. Nine of those people died.
All but two of the cases involved women aged 20 to 63, according to Germany’s medical regulator.
After a review by medical experts, the European Medicines Agency concluded the benefits of the vaccine outweighed the risks but recommended that warnings about possible rare side effects should be provided to patients and doctors.
Most European Union countries have since resumed use of the vaccine.
Dr Shelley Deeks, vice-chair of the NACI, said: “There is substantial uncertainty about the benefit of providing AstraZeneca Covid-19 vaccines to adults under 55 given the potential risks.”
She emphasised that their recommendations came amid new data from Europe which suggests that the risk of blood clots is now potentially as high as one in 100,000 – much higher than the one in 1 million believed before.
Dr Deeks said most of the patients in Europe who developed a rare blood clot after vaccination with AstraZeneca were women under 55, and the fatality rate among those who develop clots is as high as 40 per cent.
NACI’s chair, Dr Caroline Quach-Thanh, said: “This vaccine has had all the ups and downs. It looks like a rollercoaster,” while talking about the latest suspension leading to vaccine hesitancy.
Last week, Canada’s health department had changed the label on the vaccine to warn about the rare risk of blood clots.
Health Canada said it has not received any reports of blood clots, and the department’s chief medical adviser, Dr Supriya Sharma, said she still believes the vaccine’s benefits outweigh the risks.
AstraZeneca’s vaccine has come under fire for blood clot concerns and faced suspension in several countries across the world. However, its use restarted after European health regulators backed it.
It is being used in more than 70 countries across the world and is a pillar of the UN-backed project that aims to get coronavirus vaccines to poorer nations.
So far, only people aged 60 and above have received AstraZeneca’s vaccine in Ontario, which is Canada’s most populous province.
Dr David Williams, who is Ontario’s chief medical officer, said: “We have no concerns with those who have received it so far.”