Accelerated dosing interval for AstraZeneca clients

Advisory Alert

June 13, 2021

*Cette information est seulement disponible en anglais.

To: Health Care Providers


Second Dose of mRNA or AstraZeneca can be administered at an eight to 12-week interval

This Advisory Alert provides information regarding the updated acceleration of the dosing interval for individuals who received their first dose of the AstraZeneca COVID-19 vaccine. Additional guidance is provided to assist you in your practice and to facilitate informed decision-making among patients to complete the COVID-19 vaccine series.

Mixed COVID-19 vaccine schedules

As previously outlined in the June 3, 2021 Advisory Alert, individuals who received the AstraZeneca COVID-19 vaccine for their first dose, have two options to discuss with their health care provider when considering their second dose. They can opt for a second dose of AstraZeneca or choose to receive an mRNA vaccine. Both options for second doses are safe, provide strong protection against COVID-19, and will complete the COVID-19 vaccine series. Additional details and resources were also provided in the Advisory Alert dated June 11, 2021.

Dosing interval now eight to 12 weeks

On June 12, 2021 the Ministry of Health announced the further acceleration of the second dose interval for individuals who received their first dose of an AstraZeneca COVID-19 vaccine to eight weeks, with informed consent. Beginning Monday, June 14, 2021, individuals who received their first dose of the AstraZeneca vaccine will be eligible to book their second dose appointment at an interval of eight weeks or more with informed consent. Primary care providers are asked to assist patients in their informed decision-making process.

All individuals who received AstraZeneca as a first dose are eligible to receive their second dose eight to 12 weeks after their first dose regardless of which vaccine product they choose. With informed consent, individuals can choose between a second dose of AstraZeneca or an mRNA vaccine, at the eight to 12-week interval.  Recognizing that waiting 12 weeks helps to provide more protection, some may choose to receive their second dose sooner to have the increased protection provided by a second dose earlier. When mixing COVID-19 vaccines (receiving an mRNA vaccine after an AstraZeneca vaccine), a dosing interval between eight and 12 weeks is safe and effective.

Choosing to receive a second dose of AstraZeneca at an 8 to 12 week interval or choosing to receive an mRNA vaccine 8 to 12 weeks after a first dose of AstraZeneca both provide protection against COVID-19, including the Delta variant, and have been deemed safe.

Individuals who require product monograph intervals due to medical exemptions identified by the Ministry of Health can continue to book their appointment at the four to 12 week interval.

Booking instructions

Eligible individuals can book their second dose appointment by:

  1. Booking online using the provincial booking centre.
  2. Calling Public Health Sudbury & Districts at 705.674.2299 (toll-free: 1.800.708.2505), between 8 a.m. and 8 p.m., seven days a week.
  3. Contacting the pharmacy or primary care provider where they received their first dose. Visit for pharmacy locations and booking information.

Additional information and resources

Additional information on the administration of COVID-19 vaccines is available in our sample medical directives for the Pfizer BioNTech COVID-19 Vaccine  and the Moderna COVID-19 Vaccine.

For additional information on the COVID-19 vaccines, as well as for specifics on how it is being rolled out locally, please visit Public Health’s COVID-19 vaccine webpage.


Original Signed By

Dr. Penny Sutcliffe
Medical Officer of Health and Chief Executive Officer

NOTE: All Advisory Alerts are found on our website.

This item was last modified on April 22, 2024