Second Dose COVID-19 Vaccine Type-Interchangeability, Updated on June3, 2021

NACI recommends that persons who received a first dose of the AstraZeneca/COVISHIELD vaccine may receive either AstraZeneca/COVISHIELD vaccine or an mRNA vaccine (Pfizer-BioNTech or Moderna) for their second dose, unless contraindicated.

On June 1, the Public Health Agency of Canada released updated recommendations from the National Advisory Committee on Immunization (NACI) on the interchangeability of authorized COVID-19 vaccines (also referred to as ‘mixed vaccine schedules’). These recommendations are based on current scientific evidence and NACI’s expert opinion.

Persons who received a first dose of an mRNA vaccine (Pfizer-BioNTech or Moderna) should be offered the same mRNA vaccine for their second dose. If the same mRNA vaccine is not readily available or unknown, another mRNA vaccine can be considered interchangeable and should be offered to complete the vaccine series.

On June 3, 2021, the province of Ontario updated second dose guidance in alignment with the NACI’s recommendations and permitted the mixing of COVID-19 vaccines if desired. The province also supported the guidance that individuals should receive the same mRNA vaccine for their first and second doses, unless the same vaccine is not readily available. Second dose options will be provided at the recommended 12-week interval.