Ontario Proceeding with Second Dose Administration of AstraZeneca

Published on May 21, 2021

TORONTO — The Ontario government, in consultation with the Chief Medical Officer of Health and other public health experts, is proceeding with second dose administration of the AstraZeneca COVID-19 vaccine, beginning with those who received their first dose of the vaccine between March 10 and March 19, 2021.

For a limited time during the week of May 24, individuals who received their first dose of AstraZeneca during the period of March 10, 2021 to March 19, 2021 may opt for an earlier dose interval of 10 weeks with informed consent. Choosing to receive the second dose of AstraZeneca at the 10-week interval is safe and provides strong protection against COVID-19. This opportunity is being made available to ensure every vaccine dose possible is used to protect Ontarians during the effective delivery period.

Eligible individuals are encouraged to contact the pharmacy or primary care provider where they received their first dose and can book an appointment beginning the week of May 24. This will begin in the regions where the AstraZeneca vaccine was initially launched in pharmacies in March 2021. Primary care settings and pharmacies may also be reaching out to eligible Ontarians.

On May 11, 2021, following the advice of Ontario’s Chief Medical Officer of Health, Dr. David Williams, the province paused the rollout and administration of first doses of the AstraZeneca vaccine. The decision was made out of an abundance of caution due to an observed increase in an adverse reaction, known as vaccine-induced immune thrombotic thrombocytopenia (VITT), linked to the AstraZeneca vaccine. Ontario is working closely with health experts to continuously review the data for the use of AstraZeneca for first doses. The decision to pause was also based on the increased and more reliable supply of the Pfizer and Moderna mRNA vaccines and the downward trend in cases.

Nearly one million Ontarians aged 40 and over received the AstraZeneca vaccine as their first dose between March 10, 2021 and May 11, 2021. Data from the UK strongly suggests a much-reduced risk of VITT in second doses of AstraZeneca – one in 600,000. Based on this evidence, the province is committed to ensuring 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. The province is working with primary care providers and pharmacies to ensure second dose appointments are scheduled in advance of the 12-week interval, and will provide further information on how individuals who received their first dose of AstraZeneca can book a second dose appointment in the near future.

The province is also looking closely at available data and evidence from a clinical trial in the UK evaluating the administration of two doses of different vaccines and has requested direction from the National Advisory Committee on Immunization (NACI). At this time, NACI does not recommend that vaccines of different types (e.g., mRNA vaccine and viral vector vaccine) be used in the two-dose series, as data on the immune response following mixed vaccine schedules are not yet available. Further information from clinical trials and NACI’s recommendation are anticipated to be available in June 2021.

The province will provide further guidance with respect to administering doses of two different vaccines in the near future and in advance of the 12-week interval when most people are needing to receive their second dose of the AstraZeneca vaccine. When the time comes to receive a second dose, everyone who received a first dose of the AstraZeneca vaccine will receive either an AstraZeneca or mRNA vaccine for their second dose.

“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.”

As more Ontarians receive a first dose of the COVID-19 vaccine, with over 7.7 million doses administered to date, providing the second dose of the vaccine will offer the best protection possible against COVID-19 and variants, and support provincial vaccination targets as part of Ontario’s Roadmap to Reopen.

 
 
 

Quick Facts

  • As of May 20, 2021, at 8:00 p.m., over 7.7 million vaccine doses have been administered across the province, with more than 93 per cent of Ontario residents aged 80 and over and more than 89 per cent of residents aged 70 to 79 having received at least one dose. More than 59 per cent of the population aged 18 and over have received at least one dose and more than 495,000 Ontarians are fully immunized, including 96 per cent of long-term care residents.
  • In May, Ontario expects to receive approximately 4.3 million doses of COVID-19 vaccines, including 254,500 doses of AstraZeneca. Approximately 4.7 million doses of the Pfizer vaccine are expected in June. Vaccine allocations for July have not been provided at this time.
  • On May 20 the government released its Roadmap to Reopen, outlining three steps to easing public health measures, including provincial vaccination targets. Based on current trends in key health indicators, including the provincial vaccination rate, the government expects to enter Step One of the Roadmap the week of June 14, 2021.
  • Visit ontario.ca/pharmacycovidvaccine to find a pharmacy offering a COVID-19 vaccine and to book an appointment.
  • As of May 25, 2021, individuals will be able to log-in to the provincial portal through Ontario.ca to obtain a PDF copy of their COVID-19 Vaccination receipt for both their first and second dose.
  • The National Advisory Committee on Immunization (NACI) has recommended extending the vaccination dose interval up to four months for all Health Canada approved two-dose COVID-19 vaccines while maintaining a strong and sustained level of protection from the virus. Ontario has accepted and has followed NACI's recommendations as of March 10, 2021, with some limited exceptions.
  • Ontarians who are now eligible to book their vaccine appointment are asked to be patient, as it could take time to receive their vaccine. Public health units are responsible for managing and overseeing the distribution and administration of vaccines for their entire region, and public health units may have different vaccine administration rates based on local context.
 
 
 

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