MEDICAL ADVISORY: Interchangeability of Authorized COVID-19 Vaccines Issued by: M. Mustafa Hirji, MD, MPH, FRCPC, Medical Officer of Health & Commissioner (Acting) Effective June 4, 2021 in Ontario, getting the same vaccine for the first and second dose or a mixed schedule will both count as a completed series. This decision is in alignment with the updated guidance from the National Advisory Committee on Immunization (NACI). Recommendations on Interchangeability and Second Doses - Persons 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 or unknown, another mRNA vaccine is considered interchangeable and should be offered to complete the vaccine series. (Strong NACI recommendation.)
- Patients who have experienced venous or arterial thrombosis with thrombocytopenia following vaccination with a viral vector COVID-19 vaccine should not receive a second dose of a viral vector COVID-19 vaccine
- Persons who received a first dose of the AstraZeneca/COVISHIELD vaccine may receive either AstraZeneca/COVISHIELD vaccine or an mRNA vaccine for their second dose, unless contraindicated. (Discretionary NACI
recommendation.)
- Individuals can contact the pharmacy or primary care provider where they received their first dose to book a second dose of AstraZeneca 12 weeks after the first dose
- Individuals can also seek a dose of mRNA vaccine as their second dose through pharmacy or primary care at a 12 week interval
- 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 appointment” at a 12
week interval through the provincial booking system
- Following provincial guidance, if you are administering Moderna in your office, you can
- Give Moderna as a first dose to anyone 18 years of age and older
- Give Moderna as a second dose to anyone age-eligible for an accelerated second dose who received a first dose of Moderna
- Give Moderna to anyone wishing to receive an mRNA vaccine for their second dose who received AstraZeneca as a first dose and who has reached the 12-week interval
Evidence & Rationale - Similar vaccines from different manufacturers are routinely used interchangeably. For
example, different vaccine products have been used to complete a vaccine series for measles, mumps and rubella (MMRII® or Priorix®), meningococcal-C-C (Menjugate® Liquid or NeisVac-C®), and hepatitis B (Engerix®-B or Recombivax HB®), etc.
- Several European countries (Denmark, Finland, France, Germany, Sweden, Norway and Spain) have issued similar guidance to complete the two-dose COVID-19 vaccine series initiated with an AstraZeneca vaccine with a dose of an mRNA vaccine
- There is evidence that providing an mRNA vaccine after AstraZeneca vaccine will boost the immune response, which is what we expect from a second dose. There is evidence of increased short-term, mild side effects when using mixed
COVID-19 vaccine schedules, including headache, fatigue and feeling generally ill. The side effects are temporary and resolve without complications.
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