Ontario Updating AstraZeneca Second Dose Guidance

First and Second Doses of Different COVID-19 Vaccines can be Safely Combined

TORONTO — The Ontario government, in consultation with the Chief Medical Officer of Health and other health experts, is providing updated guidance for individuals who received the first dose of the AstraZeneca vaccine and who have not yet received their second dose, to allow for the mixing of COVID-19 vaccines if desired. This decision is in alignment with updated guidance from the National Advisory Committee on Immunization (NACI) recommendation.

“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, Chief Medical Officer of Health. “We are providing individuals who have received only their first dose of the AstraZeneca vaccine with two recommended options 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.”

Effective June 4, 2021 and in alignment with NACI’s recommendation, Ontarians who have received their first dose of the AstraZeneca COVID-19 vaccine can choose to either receive a second dose of the AstraZeneca vaccine, or an mRNA (Pfizer or Moderna) vaccine for their second dose. Both second-dose options available to individuals who received their first dose of the AstraZeneca vaccine are safe and provide strong protection against COVID-19 and will count as a completed series. These second dose options will be provided at the recommended 12-week interval.

Beginning June 4, 2021, individuals who received their first dose of the AstraZeneca vaccine 12 weeks ago and who would like their second dose of the AstraZeneca vaccine, can contact the pharmacy or primary care provider where they received their first dose to book an appointment. Individuals who received their first dose of the AstraZeneca vaccine and are opting to receive an mRNA vaccine have the option to schedule their second dose appointment at a participating pharmacy where the Pfizer or Moderna vaccines are administered. Primary care settings and pharmacies may also be reaching out to eligible Ontarians.

In addition, expected the week of June 7, 2021, individuals who received their first dose of the AstraZeneca vaccine and who choose to receive an mRNA vaccine for their second dose can register for a “second dose only” at a 12-week interval through the provincial booking system. Eligible individuals will also be able to schedule their second dose appointment directly through public health units that use their own booking system.

Combining similar vaccines from different manufacturers in a series is not a new concept. Different vaccine products have been safely and effectively used to complete vaccine series for influenza, hepatitis A, and others. Individuals are encouraged to speak with a health care professional for help understanding the options available to them so that they can make an informed decision on their vaccination.

NACI’s guidance also advises that the Pfizer and Moderna COVID-19 vaccines can be safely interchanged for first and second doses if the original mRNA vaccine is not readily available. Ontarians who received a first dose of an mRNA vaccine should be offered the same mRNA vaccine for their second dose. If the same mRNA vaccine is not readily available, another mRNA vaccine can be offered instead to complete the vaccine series.

All Ontarians are encouraged to get vaccinated as soon as they can, and to receive their second dose as soon as they are eligible and within the recommended interval to ensure maximum protection against COVID-19.