For more information on the study, our investigators, and how you can participate, please click here.

COVID-19 vaccination programs started in Canada in December 2020 with vaccines becoming available over the winter and into spring of 2021.  In Canada, a strategy to deliver as many first vaccine doses as possible resulted in mixed vaccine brands (giving a different second COVID-19 vaccine to the first dose) and schedules (length of time between vaccine doses) being used in many parts of the country.


Start date: December 2021

In this study, we will evaluate a third (3rd) dose of an authorized COVID-19 vaccine in adults. You do not need to have participated in MOSAIC-1 to join MOSAIC-2. If you were in MOSAIC-1 you can join MOSAIC-2.

In MOSAIC 2 we will evaluate the safety, tolerability, and immune response (resulting protection) of a third dose of a COVID-19 vaccine currently authorized in Canada (either the Pfizer-BioNTech or Moderna mRNA vaccine) in people who had two doses of COVID-19 vaccines at least six months ago.

This study is taking place at several sites across Canada. If you are interested in participating in MOSAIC or have questions, please visit the study site location page to find the appropriate contact information for your area.

You can take part if:

  1. You are 30+ years old and in good health
  2. You are available for all the study visits.
  3. You are in good health with stable health conditions.
  4. You are not pregnant.
  5. You have a record of first two doses of the authorized COVID-19 vaccines you received.

There are other study criteria that will be reviewed at the first visit to determine if you are eligible or not.


Start Date: July 2020

The initial MOSAIC study is comparing the effectiveness, safety, and acceptability of different dosing schedules of the first two doses of COVID-19 vaccines. That study began in June 2021 and is ongoing at 7 clinical sites in Canada where 195 participants were enrolled and received either both of their vaccines or the second authorized COVID-19 vaccine. Assessment is ongoing.

The study is led by the Clinical Trials Network of the Canadian Immunization Network (CIRN) and funded by the COVID-19 Immunity Task Force. It is led by Dr. Joanne Langley and Dr. Manish Sadarangani.