Canada's National Advisory Committee on Immunization (NACI) has recommended that the AstraZeneca Covid-19 vaccine should not be used in adults under 55 years of age at this time, while rare cases of serious blood clots were being further probed.
In a statement issued on Monday, the NACI said the cases, known as vaccine-induced prothrombotic immune thrombocytopenia (VIPIT), "have been recently reported in Europe following post-licensure use of the AstraZeneca Covid-19 vaccine".
"Cases identified so far have been primarily in women under the age of 55 years, although cases in men have also been reported and have mostly occurred between four and 16 days after receipt of vaccine."
The statement further said: "Following population-based analyses of VIPIT assessing risk of Covid-19 disease by age, and considering that alternate products are available (i.e., mRNA vaccines), from what is known at this time, there is substantial uncertainty about the benefit of providing AstraZeneca Covid-19 vaccine to adults under 55 years of age given that the potential risks associated with VIPIT, particularly at the lower estimated rates.
"As a precautionary measure, while Health Canada carries out an updated benefit/risk analysis based on emerging data, NACI recommends that the vaccine not be offered to adults under the age of 55.
"Adults 55 years of age and older may still be offered the AstraZeneca vaccine with informed consent, given the increased risk of hospitalisation and death due to Covid-19 in this population and since VIPIT appears to be a rarer event in that age group."
According to the Committee, the "rate of this adverse event is still to be confirmed" and information is being gathered to be more accurate.
"Anyone receiving the AstraZeneca Covid-19 vaccine should be informed of this potential adverse event and advised to seek immediate medical attention if they develop symptoms of thromboembolism and/or thrombocytopenia between days four and 20," it added.
Canada's move comes after over a dozen European countries had halted their use of the vaccine due to the blood clot issue.
Some nations have resumed vaccinations while others have continued their suspensions.
Canada has so far reported 976,327 coronavirus cases and 22,871 deaths.
Germany's medical regulator says it has received reports of 21 cases of rare blood clots in people
Meanwhile, Germany's medical regulator says it has received reports of 21 cases of rare blood clots in people who had recently received AstraZeneca's coronavirus vaccine.
The Paul Ehrlich Institute said in an email Monday to The Associated Press that seven people affected by the blood clots have died.
The incidence 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. After a review by medical experts. the European Union's medical regulator EMA recommended that warnings about possible rare side effects should be added to the vaccine information provided for patients and doctors.
Most EU countries have since resumed use of the vaccine.
The Paul Ehrlich Institute said that of the 21 cases reported in Germany until March 25, 12 also involved an abnormally low level of platelets in the patients' blood.
Of the 21 cases, 19 were in women ages 20 to 63, while two were in men ages 36 and 57.
During the period covered by the reports, some 2.27 million first doses of the AstraZeneca vaccine were administered in Germany.