Canadian province halts AZ vaccine drive over rare blood clot fears
Canada’s most populous province Ontario has halted the administration of doses of AstraZeneca (AZ) Covid-19 vaccine over concerns related to a rare adverse reaction in the form of blood clots.
The announcement that the province will no longer roll out the vaccine as part of its inoculation programme was made by its chief medical officer of health Dr David Williams.
That decision was also linked to a decreasing case load in the province as well as easier access to other vaccines as AZ supply has been constrained due to several factors including the ongoing coronavirus crisis in India.
In a statement, he said, “This decision was made out of an abundance of caution due to an observed increase in the rare blood clotting condition, known as vaccine-induced immune thrombotic thrombocytopenia (VITT), linked to the AstraZeneca vaccine.”
A total of 12 cases of this side-effects have been reported in the country so far, including three that led to death.
Federal health authorities have yet to comment on the Ontario decision.
Canada has so far received approximately 2.3 million doses of the vaccine, including 1.5 million from the United States, 500,000 manufactured by the Serum Institute of India under the Covishield brand and the remainder from the global Covax facility.
Williams pointed out that till May 8, 651,012 doses of the AstraZeneca vaccine were administered with a rate of VITT of 0.9 per 100,000 doses administered and 202,873 doses of the Covishield vaccine were administered with a rate of VITT of 1 per 100,000 doses administered. “However, over the last few days, there have been increased reports of VITT, with a rate of 1.7 per 100,000 doses administered.”
Provincial health authorities are now conferring with Health Canada and others and reviewing data to consider whether to administer the AZ jab going forward for the second dose. Among those who received the AZ injection as their first dose is Canada’s Prime Minister Justin Trudeau.
Williams also stated that data from the UK “points to a much-reduced risk of VITT in second doses of AstraZeneca”.
He also maintained that those who got their first dose in the form of the AZ vaccine “did absolutely the right thing”.
Among the options being explored is mixing vaccines, as the province awaits results of research currently underway. “The decision to pause is also based on the increased and reliable supply of the Pfizer and Moderna mRNA vaccines and the downward trend in cases. We are also seeing early promising results of administering two doses of different vaccines,” he said.