By Allison Martell and Nia Williams (NYSE:WMB)
CALGARY, Alberta (Reuters) -The Canadian provinces of Alberta and Ontario said on Tuesday they would stop offering first doses of AstraZeneca (NASDAQ:AZN)'s COVID-19 vaccine, with Ontario citing evidence that the risk of rare blood clots is somewhat higher than previously estimated.
Alberta said it took the same step only because it was unclear when more shipments of the vaccine might arrive, and not due to concern about side effects.
Officials in Ontario said roughly one in 60,000 people who received the vaccine in the province, eight in total, developed the complication, which involves blood clots accompanied by a low level of platelets, cells in the blood that help it to clot.
Regulators and expert groups in Canada, Australia, the United Kingdom and Europe had previously estimated that the risk was between one in 95,000 and one in 130,000.
"We maintain that those who received their first dose with the AstraZeneca vaccine did absolutely the right thing to prevent illness and protect their families, loved ones and communities," said Ontario's Chief Medical Officer David Williams.
Three deaths in Canada have been linked to the AstraZeneca vaccine.
Officials said the vaccine is effective, and noted that alternative vaccines from Pfizer (NYSE:PFE) and Moderna are increasingly available. Canada has distributed just over 20 million doses of various COVID vaccines, and 11.6% were AstraZeneca's vaccine.
Experts have said it is likely fine to mix COVID-19 vaccines, and a trial underway in the United Kingdom is looking at the question directly.
The news came as the western oil-producing province of Alberta struggled with a surge in COVID-19 cases. Last week the provincial government introduced new restrictions to curb infections.
In Ontario, new cases and hospitalizations are dropping but still elevated after a surge that peaked in mid-April.
Last week, Alberta reported its first case of a patient dying from a blood clot condition after receiving the AstraZeneca vaccine.
Canada's health regulator has consistently said that the vaccine's benefits outweigh any risks.
Dozens of countries have paused the use of the AstraZeneca vaccine this year after reports of rare, but serious, blood clots. Several of them have now resumed use either fully or with restrictions after health regulators said the benefits of the shot outweigh any risks.
Health Canada says those who receive the vaccine should seek medical attention immediately if they experience shortness of breath, chest pain, leg swelling, persistent belly pain, neurological symptoms like severe headaches or blurred vision, or skin bruising or tiny blood spots under the skin beyond the site of the injection.