The Government of Ontario is moving forward with administering second doses of the AstraZeneca COVID-19 vaccine.
Dr. David Williams, Ontario’s chief medical officer of health, made the announcement at a virtual press briefing on May 21.
Ontarians who received their first dose of the AstraZeneca vaccine between March 10 and 19 will be eligible to get their second dose for a limited time during the week of May 24.
Williams said that choosing to receive a second dose at this 10-week interval is safe, and will provide strong protection against COVID-19.
The recommended interval between doses is 12 weeks. The province is expediting second vaccinations so that every dose in its arsenal is used before it expires.
Eligible individuals are advised to contact the pharmacy or primary care provider where they received their first dose to book an appointment for their second dose.
Nearly one million Ontarians aged 40 and over received a dose of the AstraZeneca vaccine between March 10 and May 11, the province noted.
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Ontario paused any first doses of the AstraZeneca COVID-19 vaccine on May 11. Despite moving forward with second doses, the pause on first doses is still in place.
The decision was made “out of an abundance of caution,” after an increase in rare but serious blood clots, known as vaccine-induced immune thrombotic thrombocytopenia (VITT), was reported.
According to the provincial government, data from the UK shows that there is a greatly reduced risk of VITT with second doses of AstraZeneca.
Ontario is also closely watching a clinical trial in the UK that is evaluating mixing doses from two different vaccines.
As final data is not yet available, the National Advisory Committee on Immunization (NACI) does not recommend mixing doses at this time.
“Nothing is more important than the health of Ontarians,” Williams said.
“For the best protection against COVID-19, it is vital that everyone who received the AstraZeneca vaccine for their first dose receives a second dose of a COVID-19 vaccine.”
To date, Ontario has seen 518,980 COVID-19 cases and 8,579 virus-related deaths.