The Ontario government will proceed with second doses of the AstraZeneca COVID-19 vaccine. The first to receive their second vaccination are people initially vaccinated between March 10 to 19, 2021. These new appointments are scheduled to start the week of May 24.
Initially, AstraZeneca's second doses were to be administered 12 weeks apart. The change has reduced the interval to 10 weeks. The government stresses that this interval is safe and effective in a press release. The timetable was moved forward to ensure that all current supply is used. In May, Ontario expects to receive approximately 254,500 doses of AstraZeneca.
If you are eligible, please contact the pharmacy or primary care provider who administered your first dose starting no sooner than May 24. It is also possible that the pharmacy or primary care provider contacts eligible people.
Pharmacies and primary care settings have administered 38,000 doses as of May 21, most being AstraZeneca.
On May 11, 2021, the province paused the rollout and administration of first doses of the AstraZeneca vaccine. The pause was due to an increase in an adverse reaction, known as vaccine-induced immune thrombotic thrombocytopenia (VITT), linked to the AstraZeneca vaccine.
Ontario's health experts continue to review the first AstraZeneca dose data. Also increased and more reliable supply of the Pfizer and Moderna mRNA vaccines are available.
From March 10 to May 11, nearly one million Ontarians aged 40 and over received their first AstraZeneca dose.
UK data strongly suggests the risk of VITT is significantly lower with second doses of AstraZeneca – one in 600,000. Based on this evidence, Ontarians who received the AstraZeneca vaccine for their first dose and who do not receive their second dose at the 10-week interval during the week of May 24 will have the ability to receive a second dose of AstraZeneca within the recommended interval of 12 weeks.
For those who can not book their appointment next week, the province is working with primary care providers and pharmacies to ensure second dose appointments are scheduled in advance of the 12-week interval. Details will be explained shortly.
Clinical trial data evaluating the use of two doses of different vaccines is being reviewed. At this time, mixing different types of COVID-19 vaccines (e.g., mRNA vaccine and viral vector vaccine) is not recommended due to insufficient information. Further information from clinical trials and NACI’s recommendation are anticipated to be available in June 2021.
“Nothing is more important than the health of Ontarians, and 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,” said Dr. David Williams.
“We are providing these individuals with a safe option based on the available data and evidence and will continue to work with Health Canada to monitor the quality and efficacy of all COVID-19 vaccines being used in Ontario.”
