Mix and Match of the COVID-19 Vaccine for Safety and Immunogenicity
COVID-19
What this study involves
The registry does not currently label this study as recruiting. Ask about its status before planning a screening visit.
- Study type
- Interventional
- Phase
- Phase 2
- Age range
- 18 years - 99 years
- Sex eligible
- All sexes
- Healthy volunteers
- Accepted
- Participants
- 669 Actual
These are starting points, not an eligibility decision. The research team must review the full requirements.
About the research
The main goals of this study are to assess the immune response and safety of two different vaccines for first, second, third and fourth doses as well as for differing intervals between the first and second dose of two-dose vaccines.
Read the full description
For dose 1 and 2, the currently available mRNA vaccines (Pfizer-BioNTech BNT162b2 and Moderna mRNA-1273) are two dose vaccines which were studied in schedules of either 0 and 21 days or 0 and 28 days, respectively. The ChAdOx1 nCOV-19 (Astra-Zeneca) adenovirus-vectored vaccine is authorized to be given in two doses one month to 12 weeks apart. We will compare the interval 0, 28 days to a 0, 112 days (16 weeks) schedule, and assess the immunogenicity of both heterogeneous and heterologous second doses using the Canadian schedule.
For dose 3, the currently available mRNA vaccines (Pfizer-BioNTech BNT162b2 and Moderna mRNA-1273) and plant-based virus-like particle (Medicago Covifenz) are anticipated to be administered 6 months apart. We will assess the immunogenicity of both heterogeneous and heterologous third doses using the Canadian schedule.
For dose 4, the currently available mRNA vaccines (Pfizer-BioNTech BNT162b2 and Moderna mRNA-1273) and plant-based virus-like particle (Medicago Covifenz) are anticipated to be administered 3 months apart. We will assess the immunogenicity of both heterogeneous and heterologous third doses using the Canadian schedule.
Who may be able to participate?
The list below is the sponsor’s full registry wording. It can include conditions, prior treatment, test results and other requirements. A match in search does not mean you qualify.
Inclusion Criteria:
1. Participant is willing and able to give written informed consent to participate in the study
2. Age 18 years of age or older in good health or with mild or moderate stable co-morbidities at the time of enrolment
3. Able and willing to complete all the scheduled study procedures during the whole study follow-up period
4. If female of child-bearing potential and heterosexually active, has practiced adequate contraception for 30 days prior to injection, has a negative pregnancy test on the day of injection, and has agreed to continue adequate contraception until 3 months after the final dose of study vaccine (Please refer to the definition section for a description of child-bearing potential and adequate contraception)
5. MOSAIC-1 Vaccine-exposed subgroups: have received or are booked to receive the first dose of an authorized COVID-19 vaccine in the 55 days prior to Visit 1 (documentation of receipt required)
6. MOSAIC -1 Vaccine naïve subgroups: have not received an authorized COVID-19 vaccine at any time
7. MOSAIC-2 participants have received two doses of COVID-19 vaccines authorized in Canada ≥6 months prior to study vaccine administration (documentation of receipt required)
8. MOSAIC-3 participants have received three doses of COVID-19 vaccines authorized in Canada ≥3 months prior to study vaccine administration (documentation of receipt required)
Exclusion Criteria:
1. Inability or unwillingness of participant or legally acceptable representative to give written informed consent
2. Any confirmed or suspected immunosuppressive or immunodeficient state; asplenia, or immunosuppressant medication within the past 6 months except short term oral steroids (≤14 days duration) or topical steroids
3. Current diagnosis or treatment for cancer (except basal cell carcinoma of the skin)
4. Administration of immunoglobulins and/or any blood products within 3 months preceding the first dose of study vaccine and for one month after the last dose of study vaccine
5. Allergy to any study vaccine or any active substance in a study vaccine
6. Bleeding disorder or history of significant bleeding following IM injections or venipuncture
7. Continuous use of anticoagulants
8. A history of anaphylaxis to a previous vaccine
9. Pregnancy or intent to become pregnant during the study or within 3 months of the last dose of study vaccine
10. MOSAIC-1: History of laboratory-confirmed COVID-19 disease prior to enrolment by participant report
11. Administration of a live virus vaccine within 4 weeks prior to study vaccine receipt.
Treatment, groups and participation
The registry may describe treatments and study duration without a complete visit calendar. Ask the study team for the exact schedule, procedures, risks, costs and alternatives. Keep your usual care plan unless your treating clinician tells you otherwise.
- Assignment
- Random assignment
- Masking
- Triple masked
Group 1: Moderna, Moderna - 28 Days apart
Participants will be blinded and receive two doses (0.20 mg/mL each) of mRNA-1273 SARS-CoV-2 vaccine via intramuscular injection in the deltoid muscle 28 days apart.
Vaccine-exposed participants will only be blinded to, and receive, the second injection.
Biological: mRNA-1273 SARS-CoV-2 vaccine · Other: 0, 28 day schedule
Group 2: Moderna, Moderna - 112 days apart
Participants will be blinded and receive two doses (0.20 mg/mL each) of mRNA-1273 SARS-CoV-2 vaccine at 0.20 mg/mL via intramuscular injection in the deltoid muscle 112 days apart.
Vaccine-exposed participants will only be blinded to, and receive, the second injection.
Biological: mRNA-1273 SARS-CoV-2 vaccine · Other: 0, 112 day schedule
Group 3: Moderna, Pfizer/BioNTech - 28 days apart
Participants will be blinded and receive one dose (0.20 mg/mL) of mRNA-1273 SARS-CoV-2 vaccine via intramuscular injection in the deltoid muscle followed by one dose (0.3mL) of BNT162b2 vaccine after 28 days.
Vaccine-exposed participants will only be blinded to, and receive, the second injection.
Biological: mRNA-1273 SARS-CoV-2 vaccine · Biological: BNT162b2 · Other: 0, 28 day schedule
Group 4: Moderna, Pfizer/BioNTech - 112 days apart
Participants will be blinded and receive one dose (0.20 mg/mL) of mRNA-1273 SARS-CoV-2 vaccine via intramuscular injection in the deltoid muscle followed by one dose (0.3mL) of BNT162b2 vaccine after 112 days.
Vaccine-exposed participants will only be blinded to, and receive, the second injection.
Biological: mRNA-1273 SARS-CoV-2 vaccine · Biological: BNT162b2 · Other: 0, 112 day schedule
Group 5: Pfizer/BioNTech, Pfizer/BioNTech - 28 days apart
Participants will be blinded and receive two doses (0.3mL each) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle 28 days apart.
Vaccine-exposed participants will only be blinded to, and receive, the second injection.
Biological: BNT162b2 · Other: 0, 28 day schedule
Group 6: Pfizer/BioNTech, Pfizer/BioNTech - 112 days apart
Participants will be blinded and receive two doses (0.3mL each) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle 112 days apart.
Vaccine-exposed participants will only be blinded to, and receive, the second injection.
Biological: BNT162b2 · Other: 0, 112 day schedule
Group 7: Pfizer/BioNTech, Moderna - 28 days apart
Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle followed by one dose (0.20 mg/mL) of mRNA-1273 SARS-CoV-2 vaccine after 28 days.
Vaccine-exposed participants will only be blinded to, and receive, the second injection.
Biological: mRNA-1273 SARS-CoV-2 vaccine · Biological: BNT162b2 · Other: 0, 28 day schedule
Group 8: Pfizer/BioNTech, Moderna - 112 days apart
Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle followed by one dose (0.20 mg/mL) of mRNA-1273 SARS-CoV-2 vaccine after 112 days.
Vaccine-exposed participants will only be blinded to, and receive, the second injection.
Biological: mRNA-1273 SARS-CoV-2 vaccine · Biological: BNT162b2 · Other: 0, 112 day schedule
Group 9: Astra Zeneca, Moderna - 28 days apart
Participants will be blinded and receive one dose (0.5 ml) of ChAdOx1-S \[recombinant\] vaccine via intramuscular injection in the deltoid muscle followed by one dose (0.20 mg/mL) of mRNA-1273 SARS-CoV-2 vaccine after 28 days.
Vaccine-exposed participants will only be blinded to, and receive, the second injection.
Biological: mRNA-1273 SARS-CoV-2 vaccine · Biological: ChAdOx1-S [recombinant] · Other: 0, 28 day schedule
Group 10: Astra Zeneca, Moderna - 112 days apart
Participants will be blinded and receive one dose (0.5 ml) of ChAdOx1-S \[recombinant\] vaccine via intramuscular injection in the deltoid muscle followed by one dose (0.20 mg/mL) of mRNA-1273 SARS-CoV-2 vaccine after 112 days.
Vaccine-exposed participants will only be blinded to, and receive, the second injection.
Biological: mRNA-1273 SARS-CoV-2 vaccine · Biological: ChAdOx1-S [recombinant] · Other: 0, 112 day schedule
Group 11: Astra Zeneca, Pfizer/BioNTech - 28 days apart
Participants will be blinded and receive one dose (0.5 ml) of ChAdOx1-S \[recombinant\] vaccine via intramuscular injection in the deltoid muscle followed by one dose (0.3 mL) of BNT162b2 vaccine after 28 days.
Vaccine-exposed participants will only be blinded to, and receive, the second injection.
Biological: BNT162b2 · Biological: ChAdOx1-S [recombinant] · Other: 0, 28 day schedule
Group 12: Astra Zeneca, Pfizer/BioNTech - 112 days apart
Participants will be blinded and receive one dose (0.5 ml) of ChAdOx1-S \[recombinant\] vaccine via intramuscular injection in the deltoid muscle followed by one dose (0.3 mL) of BNT162b2 vaccine after 112 days.
Vaccine-exposed participants will only be blinded to, and receive, the second injection.
Biological: BNT162b2 · Biological: ChAdOx1-S [recombinant] · Other: 0, 112 day schedule
Group 1b
Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle.
Biological: BNT162b2
Group 2b
Participants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle.
Biological: mRNA-1273 SARS-CoV-2 vaccine
Group 3b
Participants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle.
Biological: mRNA-1273 SARS-CoV-2 vaccine
Group 4b
Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle.
Biological: BNT162b2
Group 5b
Participants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle.
Biological: mRNA-1273 SARS-CoV-2 vaccine
Group 6b
Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle.
Biological: BNT162b2
Group 7b
Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle.
Biological: BNT162b2
Group 8b
Participants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle.
Biological: mRNA-1273 SARS-CoV-2 vaccine
Group 9b
Participants will receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle.
Biological: Covifenz
Group 1c
Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle.
Biological: BNT162b2
Group 2c
Participants will be blinded and receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle.
Biological: Covifenz
Group 3c
Participants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle.
Biological: mRNA-1273 SARS-CoV-2 vaccine
Group 4c
Participants will be blinded and receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle.
Biological: Covifenz
Group 5c
Participants will be blinded and receive either one dose (0.3mL) of BNT162b2 or one half dose (0.25mL) of mRNA-1273 via intramuscular injection in the deltoid muscle.
Biological: mRNA-1273 SARS-CoV-2 vaccine · Biological: BNT162b2
Group 6c
Participants will be blinded and receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle.
Biological: Covifenz
Group 7c
Participants will receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle.
Biological: Covifenz
mRNA-1273 SARS-CoV-2 vaccine BIOLOGICAL
Contains 1.26 mg of CX-024414 mRNA and 24.38 mg of SM-102 LNP as a white to off-white dispersion in preservative-free diluent buffer at pH 7.5.
BNT162b2 BIOLOGICAL
A white to off-white, sterile, preservative-free, frozen suspension for intramuscular injection, supplied with 0.9% sodium chloride diluent for injection plastic ampoules.
ChAdOx1-S [recombinant] BIOLOGICAL
A colourless to slightly brown, clear to slightly opaque solution containing 5 x 1010 viral particles (not less than 2.5 x 108 infectious units).
0, 28 day schedule OTHER
Second injection administered 28 days post first injection
0, 112 day schedule OTHER
Second injection administered 112 days post first injection
Covifenz BIOLOGICAL
COVIFENZ is an emulsion for intramuscular injection. The 3.75 mcg antigen component of COVIFENZ is a suspension, which must be mixed 1:1 with the 0.25 mL AS03 adjuvant emulsion component prior to administration
What researchers are measuring
Outcome measures describe what is being studied. They are not proof that a treatment works.
Primary measures
Antibody response to SARS-CoV-2 S protein after 2 doses
Time frame: Day 56
The co-primary outcome for the non-inferiority comparison of 0, 28-day schedules with heterologous second dose is the immune response to SARS-CoV-2 at day 56 (28 days after the second dose of vaccine) based on anti-spike antibody titers.
Antibody response to SARS-CoV-2 S protein after 2 doses
Time frame: Day 140
The co-primary outcome for the non-inferiority comparison of schedules in which the timing of the second dose of vaccine is different (0, 28 days v 0, 112 days) is the immune response to SARS-CoV-2 at day 140 (28 days after the last dose in the 0, 112 day schedule) based on anti-spike antibody titers.
Antibody response to SARS-CoV-2 S protein after 3 doses
Time frame: Day 28
To determine if a vaccination schedule with a heterologous third dose of a COVID-19 vaccine induces a non-inferior serum immune response to SARS-CoV-2, compared to a third dose/booster with a homologous vaccine.
Antibody response to SARS-CoV-2 S protein after 4 doses
Time frame: Day 28
To determine if a vaccination schedule with a heterologous fourth dose of a COVID-19 vaccine induces a non-inferior serum immune response to SARS-CoV-2, compared to a third dose/booster with a homologous vaccine.
Secondary measures
Durability of antibody response to SARS-CoV-2 S over 12 months after 2 doses
Time frame: Baseline and Days 28, 56, 112, 140, 365
Assess durability of immune responses in each study group over 12 months based on anti-spike antibody titers and pseudoneutralization assay.
Pseudoneutralization assay, T cell testing, Antibody dependent cellular cytotoxicity (ADCC), Antibody avidity, RNA seq after 2 doses
Time frame: Days 28, 56, 112, 140, 365
Characterization of the immune response to COVID-19 vaccines in schedules with 0, 28 days versus 0, 112 days dosing and heterologous schedules to day 365.
Incidence of grade 3 solicited local and systemic adverse events, SAEs, AEFIs, MAAEs, AESIs in the 7 days following vaccine receipt after 2 doses
Time frame: From time of first study injection through Day 365.
Description of safety outcomes over 12 months post-vaccination including SAEs (serious adverse events), provincially reportable AEFIs (adverse events following immunization), MAAEs (medically attended adverse events), AESIs (adverse events of special interest).
Incidence of grade 3 solicited local and systemic adverse events, SAEs, AEFIs, MAAEs, AESIs in the 7 days following vaccine receipt after 3 doses
Time frame: From time of first study injection through Day 365.
Description of safety outcomes over 12 months post-vaccination including SAEs (serious adverse events), provincially reportable AEFIs (adverse events following immunization), MAAEs (medically attended adverse events), AESIs (adverse events of special interest).
Acceptability of vaccines as determined by participant-completed questionnaire after 2 doses
Time frame: Days 56, 140, and 365
Four 5 point likert scale type questions asking whether they would want to receive the vaccine again, recommend it to a friend, whether they were anxious about receiving it, and whether they would prefer a more painful injection if it conferred better protection.
Acceptability of vaccines as determined by participant-completed questionnaire after 3 doses
Time frame: Days 28, 180
Four 5 point likert scale type questions asking whether they would want to receive the vaccine again, recommend it to a friend, whether they were anxious about receiving it, and whether they would prefer a more painful injection if it conferred better protection.
Antibody to SARS-CoV-2 S and N, RBD after 3 doses
Time frame: Days 180 and 365
Assess durability of the immune responses in each study group over 12 months after the study vaccine.
Pseudoneutralization assay, T cell testing, Antibody dependent cellular cytotoxicity after 3 doses
Time frame: Day 365
Further characterize the immune response to COVID-19 vaccine in schedules with homologous and heterologous third doses to day 365
Incidence of grade 3 solicited local and systemic adverse events, SAEs, AEFIs, MAAEs, AESIs in the 7 days following vaccine receipt after 4 doses
Time frame: From time of first study injection through Day 365.
Description of safety outcomes over 12 months post-vaccination including SAEs (serious adverse events), provincially reportable AEFIs (adverse events following immunization), MAAEs (medically attended adverse events), AESIs (adverse events of special interest).
Acceptability of vaccines as determined by participant-completed questionnaire after 4 doses
Time frame: Days 28, 180
Four 5 point likert scale type questions asking whether they would want to receive the vaccine again(Yes, definitely; Yes, probably; I don't know; No, probably not; No, definitely not), recommend it to a friend(Yes, definitely; Yes, probably; I don't know; No, probably not; No, definitely not), whether they were anxious about receiving it(Not at all; A little; Moderately; Very; Extremely), and whether they would prefer a more painful injection if it conferred better protection(Vaccine A; Vaccine B; No preference; Unsure/don't know).
Antibody to SARS-CoV-2 S and N, RBD after 4 doses
Time frame: Days 180 and 365
Assess durability of the immune responses in each study group over 12 months after the study vaccine.
Antibody dependent cellular cytotoxicity after 4 doses
Time frame: Day 365
Further characterize the immune response to COVID-19 vaccine in schedules with homologous and heterologous third doses to day 365
Pseudoneutralization assay after 4 doses
Time frame: Day 365
Measuring the 50% Neutralization Titer to further characterize the immune response to COVID-19 vaccine in schedules with homologous and heterologous third doses to day 365
T cell testing after 4 doses
Time frame: Day 365
Measuring the number of T cells to further characterize the immune response to COVID-19 vaccine in schedules with homologous and heterologous third doses to day 365
Other measures
Exploratory assessment of interval between dose 1 and 2 on immune response after 3 or 4 doses
Time frame: From time of first study injection through Day 365.
Assess the role of intervals between first and second doses of the primary immunization schedule, and between 2nd and 3rd doses, on immune responses after the third dose over the study period.
Review the complete result tables and limitations in the official record.
Open official results ↗Research locations (8)
The overall study status and a local site’s status can differ. Confirm that location’s availability before traveling.
8 locations
Royal Inland HospitalKamloops, British Columbia, CanadaStatus unknown
Penticton Regional HospitalPenticton, British Columbia, CanadaStatus unknown
BC Children's Hospital Research InstituteVancouver, British Columbia, CanadaStatus unknown
Children's Hospital Research Institute of ManitobaWinnipeg, Manitoba, CanadaStatus unknown
Canadian Center for VaccinologyHalifax, Nova Scotia, CanadaStatus unknown
Ottawa Hospital Research Institute, University of OttawaOttawa, Ontario, CanadaStatus unknown
McGill University Health Centre Vaccine Study CentreMontreal, Quebec, CanadaStatus unknown
CHU de Québec, Université LavalQuébec, Quebec, CanadaStatus unknown
Study team and timeline
- Lead sponsor
- Canadian Immunization Research Network
- Study start
- Jun 11, 2021 Actual
- Primary completion
- Jul 25, 2022 Actual
- Study completion
- Jun 16, 2023 Actual
- First posted
- May 20, 2021 Actual
- Last updated
- Nov 10, 2026 Actual
Official study contacts
No central contact is listed. Check the locations and the official record.
Official study title
Immunogenicity and Adverse Events Following Immunization (AEFI) With Alternate Schedules of COVID-19 Vaccines in Canada: is "Mix and Match" of the Second Dose (MOSAIC-1;CT24a) and Additional Doses (MOSAIC-2 and MOSAIC-3;CT24b and CT24c) Safe and Immunogenic?
Ask Wellness Clinical Research
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Source: ClinicalTrials.gov API v2. Information is submitted by sponsors and investigators. NLM does not approve the safety or science of all listed studies. Registry disclaimer.
Retrieved: Nov 12, 2026 · Last registry update: Nov 10, 2026
