TORONTO -- A new Canada-wide study will look at the effect of using different COVID-19 vaccine doses in Canadian adults to determine if mixing and matching vaccines yields a strong immune response and how long the response lasts.
The study, announced Thursday, will investigate the use of different vaccines for first and second doses in 1,300 adult participants. The study will be conducted in conjunction with the COVID-19 Immunity Task Force, Vaccine Surveillance Reference Group, Canadian Immunization Research Network and Dalhousie University.
"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?" said Dr. Joanne Langley, co-principal investigator of the study and professor at Dalhousie University, said in a press release.
The study will also work to determine the immune response created by mixing and matching vaccines, and how long the immune response will last.
The study, called "Mix and match of the second COVID-19 vaccine dose for safety and immunogenicity," or MOSAIC for short, will begin enrolling participants as soon as possible at Canadian Immunization Research Network clinical trial sites. These sites are located in Nova Scotia, Quebec, Ontario, Manitoba, Alberta and B.C.
There are currently four vaccines authorized for emergency use in Canada. However, several provinces have suspended the use of the AstraZeneca COVID-19 vaccine for first doses over concerns of rare blood clots.
Canada's own vaccine is still in phase three trials, but could be added to the study pending authorization.
"As other vaccines come 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," Dr. Manish Sadarangani, co-principal investigator of the study and associate professor at the University of British Columbia, said in the release.
Currently, Canada's National Advisory Committee on Immunization recommends an interval between COVID-19 vaccine doses of up to four months, except in high risk individuals, to ensure as many people get a first dose as possible. This study aims to help guide future vaccine rollout plans, the release said.
Other countries are also running clinical trials to see if mix and matching vaccine doses is safe.
Preliminary results from both a U.K. and a Spanish study suggest that the combination is ultimately safe and that the mixed schedule of doses seemed to jolt the immune system into producing many more antibodies.
"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," Dr. Theresa Tam, Canada's Chief Public Health Officer, said in a press release.
People 18 years of age or older can participate in the study by .
