The National Advisory Committee on Immunization (NACI) has recommended that the AstraZeneca COVID-19 vaccine not be used in adults under the age of 55.
Officials from NACI and Health Canada announced the decision at a press conference on Monday afternoon.
The suspension is a precautionary measure while rare cases of serious blood clots following immunization with the AstraZeneca vaccine are investigated.
This adverse event, called vaccine-induced prothrombotic immune thrombocytopenia (VIPIT), has occurred primarily in women under 55, the vice-chair of NACI, Dr. Shelley Deeks, said.
The condition tends to occur between four and 16 days after vaccination.
“Right now, we do not know with certainty the rate of this adverse event,” Deeks said.
European regulators originally estimated that VIPIT occurs in approximately one in every one million people immunized with the AstraZeneca COVID-19 vaccine.
However, the Paul-Ehrlich-Institut, a regulatory body in Germany, has reported that the condition occurs in one out of every 100,000 people.
Based on available information, Deeks said the fatality of the condition is approximately 40%. She cautioned this number might decrease as awareness of VIPIT increases.
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“NACI recommends that the vaccine not be used in adults under the age of 55 years,” Deeks announced.
The decision was based on a population-based analysis that considered what officials know about VIPIT, the risks of COVID-19 in Canada by age, and the alternate vaccines available in the country.
Adults over the age of 55 can still receive the AstraZeneca COVID-19 vaccine, as VIPIT appears to be rarer in older adults, and their risk of severe disease is greater, Deeks said.
“From what is known at this time, there is substantial uncertainty about the benefit of providing AstraZeneca vaccine to adults under 55 years of age, given the potential risks associated with VIPIT,” said Dr. Howard Njoo, Canada’s deputy chief public health officer.
“At this time, we are pausing the use of AstraZeneca vaccine to adults under 55 years of age pending further risk-benefit analysis.”