New Canada-Wide Research to Study Mixing-and-Matching COVID-19 vaccines

The Government of Canada, through the COVID-19 Immunity Task Force (CITF) and the Vaccine Surveillance Reference Group (VSRG), is supporting a new nation-wide study that will look at the effects of ‘mixing-and-matching’ approved COVID-19 vaccines in adults. Approximately $4.8 million is being provided for this study, which will assess the safety and effectiveness of using two different COVID-19 vaccines for the first and second dose. The project will also study the effects of increasing the interval between doses.

“As questions of vaccine interchangeability arise and alternative dosing intervals are being used in public health programs, our objective is to determine: what are the effects of different dosing intervals of the vaccines on immunity and safety?” explains Dr. Joanne Langley, co-Principal Investigator (PI) of this research project. She is also lead investigator of the Canadian Immunization Research Network’s (CIRN) Clinical Trials Network and a Professor in the Departments of Pediatrics and Community Health and Epidemiology at Dalhousie University. “We also want to know what the immune response is if two doses of different COVID-19 vaccine products are used, and how long these responses last.”

The study, entitled “Mix and match of the second COVID-19 vaccine dose for SAfety and ImmunogeniCity,” or MOSAIC, is expected to enroll 1,300 participants as soon as possible across CIRN clinical trial sites in Nova Scotia, Quebec, Ontario, Manitoba, Alberta and British Columbia.

“There are currently four COVID-19 vaccines approved for use in Canada, three of which are being distributed by public health programs,” says co-PI Dr. Manish Sadarangani, an Associate Professor in the Department of Pediatrics at the University of British Columbia and Director at the Vaccine Evaluation Center at BC Children’s Hospital. “As other vaccines become available, they will be added to the study to address public health knowledge gaps. Study data will be communicated regularly to public health officials to help inform decision making for the ongoing vaccine rollout in Canada.”

“Soon after vaccine programs began, manufacturing interruptions resulted in delayed vaccine shipments to various countries, including Canada,” states Dr. Scott Halperin, co-Chair of the VSRG and Principal Investigator of CIRN. “This led some provinces to change their vaccine delivery strategies, including following the National Advisory Committee on Immunization’s (NACI) approved guidelines to allow second-dose immunizations to occur up to four months after the first dose, rather than the 21- to 28-day period recommended by manufacturers. This study will give public health officials more information about how to manage their vaccine roll-out strategies going forward.”

“Studies on mixed COVID-19 vaccine schedules are underway in other countries, including the United Kingdom. In addition to international data, this Canadian study will help inform Canada’s public health recommendations on the potential to use different combinations of vaccines for the first and second dose, as well as different dosing intervals,” says Dr. Theresa Tam, Canada’s Chief Public Health Officer.

“There has never been a more critical time to collect real-time evidence to inform practice, policy, and decision making,” says Dr. Alice Aiken, Vice President Research and Innovation at Dalhousie University. “We are very proud of Dr. Joanne Langley, and the important work she is doing to ensure we are using vaccines the most effective way possible, and to help stop the spread of COVID-19.”

If you are 18 years or older, in good health, and would like to participate in the study, please visit for more information.

About the Canadian Immunization Research Network

The Canadian Immunization Research Network (CIRN) is a national network of key vaccine researchers who develop and test methodologies related to the evaluation of vaccines as they pertain to safety, immunogenicity and effectiveness, and program implementation and evaluation. CIRN’s objective is to further strengthen Canada’s research capacity, evidence base and expertise in the field of immunization and vaccines for vaccine-preventable diseases. A ‘network or networks’, CIRN plays a pivotal role in mentoring early-career researchers, recruiting new investigators, providing opportunities for trainees, and delivering meaningful engagement of stakeholders at all research stages.

CIRN is made up of the following 8 networks: the Canadian National Vaccine Safety Network (CANVAS); the Clinical Trials Network (CTN); the Serious Outcomes Surveillance Network (SOS); the Special Immunization Clinic Network (SIC); the Provincial Collaborative Network (PCN); the Social Sciences and Humanities Network (SSHN); the Modeling and Economics Research Network (ModERN); and the Reference Laboratory Network (RLN).

About Dalhousie University

Dalhousie University is Atlantic Canada’s leading research-intensive university. Located in the heart of Halifax, Nova Scotia, with an Agricultural Campus in Truro/Bible Hill, Dalhousie is a truly national and international university, with more than half of the university’s 20,000-plus students coming from outside the province. Dal’s 6,000 faculty and staff foster a diverse, purpose-driven community, one that spans 13 faculties and conducts more than $181 million in research annually. Part of a cluster identified as one of the world’s top international centres in ocean research, the university proudly celebrated its 200th anniversary in 2018.

About the Vaccine Surveillance Reference Group

The Vaccine Surveillance Reference Group (VSRG) supports the monitoring of the safety and effectiveness of COVID-19 vaccines in Canada. It is a consortium of Canadian organizations – the Public Health Agency of Canada (PHAC), the Canadian Research Immunization Network (CIRN), the National Advisory Committee on Immunization (NACI), and the COVID-19 Immunity Task Force (CITF) – working collaboratively to pool expertise on vaccine surveillance. The VSRG reports to PHAC and is supported by the CITF Secretariat. It is co-chaired by the leaders of NACI and CIRN. Among its responsibilities, the VSRG, through the CITF Executive Committee, makes recommendations to PHAC on funding research teams that can address important aspects of the immune response, safety, and effectiveness of COVID-19 vaccines with public health relevance and with attention to all priority groups. For more information visit:

About the COVID Immunity Task Force (CITF)

In late April 2020, the Government of Canada established the COVID-19 Immunity Task Force with a two-year mandate. The Task Force is overseen by a Leadership Group of volunteers that includes leading Canadian scientists and experts from universities and healthcare facilities across Canada who are focused on understanding the nature of immunity arising from the novel coronavirus that causes COVID-19. To that end, the CITF is supporting numerous studies to determine the extent of SARS-CoV-2 infection in Canada (in the general population as well as in specific communities and priority populations), understand the nature of immunity following infection, develop improved antibody testing methods, and help monitor the effectiveness and safety of vaccines as they are rolled out across Canada. The Task Force and its Secretariat accordingly work closely with a range of partners, including governments, public health agencies, institutions, health organizations, research teams, other task forces, and engages communities and stakeholders. Most recently, the Task Force has been asked to support vaccine surveillance, effectiveness and safety as part of its overall objective to generate data and ideas that inform interventions aimed at slowing – and ultimately stopping – the spread of SARS-CoV-2 in Canada. For more information visit:

Media contacts:

To speak to one of the study researchers:
Olivia Kwiecien
Program Communications, Canadian Immunization Research Network (CIRN)
Cell: +1.902.292.1726

To speak to a member of the CITF/VSRG:
Rebecca Burns, Cell: +1.438.871.8763
Caroline Phaneuf, Cell: +1.514.444.4532