The Canadian government signed a contract with AstraZeneca in 2020 to get 20 million doses of its vaccine, and 2.3 million Canadians were inoculated with it, mostly between March and June 2021.

Following concerns in the spring of 2021 about rare but potentially fatal blood clots from AstraZeneca, Canada moved its focus to using its ample supplies of the mRNA vaccines from Pfizer and Moderna.

In July 2021, Canada promised to donate the rest of its supply, about 17.7 million doses.

But in a statement on Tuesday, Health Canada said despite efforts to meet that pledge, 13.6 million doses have expired and will have to be thrown out.

"Due to limited demand for the vaccine and recipient country challenges with distribution and absorption, they were not accepted,'' the statement said.

In all, Canada donated 8.9 million doses of AstraZeneca vaccine - 4.8 millon doses from its main supply and 4.1 million doses it bought from the COVAX vaccine-sharing program.

About 85 per cent of Canadians are considered fully vaccinated, compared with 61 per cent of the world's population - and just 16 per cent of people living in the world's poorest countries.

Australian Associated Press