COVID-19Phase 2MOSAICNCT04894435

Mix and Match of the COVID-19 Vaccine for Safety and Immunogenicity

A Phase 2 study testing mRNA-1273 SARS-CoV-2 vaccine, BNT162b2 and ChAdOx1-S [recombinant] in people with COVID-19, run by Canadian Immunization Research Network at 8 sites in Canada.

Active, not recruiting

Under way, not looking for participants. Everyone needed has enrolled. The study is still running.

Official record

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Trial summary

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 more about this study

Who is it for?: Ages 18 to 99 yearsHealthy volunteers can take part
Conditions the study is for: COVID-19
What is being tested?: mRNA-1273 SARS-CoV-2 vaccine, BNT162b2 and ChAdOx1-S [recombinant]
Type of treatment: Vaccines, Injection or infusion
Could I receive a placebo?: No, everyone receives an active treatment
How many people: 669 participants
Where: 8 sitesCanada
Study dates: 20 May 2021to 1 Aug 2025
Phase: Phase 2
Are there results?: Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

Ages 18 to 99 years
All sexes
Healthy volunteers accepted
Adult, Older adult

Who may be able to join

Participant is willing and able to give written informed consent to participate in the study
Age 18 years of age or older in good health or with mild or moderate stable co-morbidities at the time of enrolment
Able and willing to complete all the scheduled study procedures during the whole study follow-up period
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)
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)
MOSAIC -1 Vaccine naïve subgroups: have not received an authorized COVID-19 vaccine at any time
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)
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)

Who cannot join

Inability or unwillingness of participant or legally acceptable representative to give written informed consent
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
Current diagnosis or treatment for cancer (except basal cell carcinoma of the skin)
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
Allergy to any study vaccine or any active substance in a study vaccine
Bleeding disorder or history of significant bleeding following IM injections or venipuncture

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Continuous use of anticoagulants
A history of anaphylaxis to a previous vaccine
Pregnancy or intent to become pregnant during the study or within 3 months of the last dose of study vaccine
MOSAIC-1: History of laboratory-confirmed COVID-19 disease prior to enrolment by participant report
Administration of a live virus vaccine within 4 weeks prior to study vaccine receipt.

Trial locations and contacts

8 sites in 1 country.

City, postcode or hospital

8 sites in 1 country

Canada8 sites

Canadian Center for Vaccinology
Halifax, Nova Scotia
Royal Inland Hospital
Kamloops, British Columbia
McGill University Health Centre Vaccine Study Centre
Montreal, Quebec, H9H 4Y6
Ottawa Hospital Research Institute, University of Ottawa
Ottawa, Ontario
Penticton Regional Hospital
Penticton, British Columbia
CHU de Québec, Université Laval
Québec, Quebec
BC Children's Hospital Research Institute
Vancouver, British Columbia, V5Z 4H4
Children's Hospital Research Institute of Manitoba
Winnipeg, Manitoba

Other trials in Canada

About this study

Official 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?

Read the detailed 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.

Conditions: COVID-19
Being tested: mRNA-1273 SARS-CoV-2 vaccine, BNT162b2, ChAdOx1-S [recombinant], 0, 28 day schedule, 0, 112 day schedule
Keywords: SARS-CoV-2, vaccine, clinical trial
Medical subject headings: COVID-19

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

mRNA-1273 SARS-CoV-2 vaccineBiological
Also called COVID-19 Vaccine Moderna, Spikevax
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.
BNT162b2Biological
Also called Pfizer-BioNTech COVID-19 Vaccine, Comirnaty
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
Also called Astra Zeneca COVID-19 Vaccine, COVISHIELD AstraZeneca COVID-19 Vaccine, Vaxzevria
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 scheduleOther
Second injection administered 28 days post first injection
0, 112 day scheduleOther
Second injection administered 112 days post first injection
CovifenzBiological
Also called Medicago COVID-19 vaccine
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

Study groups in NCT04894435
Study group	Role	What they receive
Group 1: Moderna, Moderna - 28 Days apart	Active comparator	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. Receives: Biological: mRNA-1273 SARS-CoV-2 vaccine; Other: 0, 28 day schedule
Group 2: Moderna, Moderna - 112 days apart	Active comparator	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. Receives: Biological: mRNA-1273 SARS-CoV-2 vaccine; Other: 0, 112 day schedule
Group 3: Moderna, Pfizer/BioNTech - 28 days apart	Active comparator	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. Receives: Biological: mRNA-1273 SARS-CoV-2 vaccine; Biological: BNT162b2; Other: 0, 28 day schedule
Group 4: Moderna, Pfizer/BioNTech - 112 days apart	Active comparator	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. Receives: Biological: mRNA-1273 SARS-CoV-2 vaccine; Biological: BNT162b2; Other: 0, 112 day schedule
Group 5: Pfizer/BioNTech, Pfizer/BioNTech - 28 days apart	Active comparator	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. Receives: Biological: BNT162b2; Other: 0, 28 day schedule
Group 6: Pfizer/BioNTech, Pfizer/BioNTech - 112 days apart	Active comparator	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. Receives: Biological: BNT162b2; Other: 0, 112 day schedule
Group 7: Pfizer/BioNTech, Moderna - 28 days apart	Active comparator	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. Receives: Biological: mRNA-1273 SARS-CoV-2 vaccine; Biological: BNT162b2; Other: 0, 28 day schedule
Group 8: Pfizer/BioNTech, Moderna - 112 days apart	Active comparator	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. Receives: Biological: mRNA-1273 SARS-CoV-2 vaccine; Biological: BNT162b2; Other: 0, 112 day schedule
Group 9: Astra Zeneca, Moderna - 28 days apart	Active comparator	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. Receives: Biological: mRNA-1273 SARS-CoV-2 vaccine; Biological: ChAdOx1-S [recombinant]; Other: 0, 28 day schedule
Group 10: Astra Zeneca, Moderna - 112 days apart	Active comparator	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. Receives: 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	Active comparator	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. Receives: Biological: BNT162b2; Biological: ChAdOx1-S [recombinant]; Other: 0, 28 day schedule
Group 12: Astra Zeneca, Pfizer/BioNTech - 112 days apart	Active comparator	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. Receives: Biological: BNT162b2; Biological: ChAdOx1-S [recombinant]; Other: 0, 112 day schedule
Group 1b	Active comparator	Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: BNT162b2
Group 2b	Active comparator	Participants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: mRNA-1273 SARS-CoV-2 vaccine
Group 3b	Active comparator	Participants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: mRNA-1273 SARS-CoV-2 vaccine
Group 4b	Active comparator	Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: BNT162b2
Group 5b	Active comparator	Participants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: mRNA-1273 SARS-CoV-2 vaccine
Group 6b	Active comparator	Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: BNT162b2
Group 7b	Active comparator	Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: BNT162b2
Group 8b	Active comparator	Participants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: mRNA-1273 SARS-CoV-2 vaccine
Group 9b	Experimental	Participants will receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: Covifenz
Group 1c	Active comparator	Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: BNT162b2
Group 2c	Active comparator	Participants will be blinded and receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: Covifenz
Group 3c	Active comparator	Participants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: mRNA-1273 SARS-CoV-2 vaccine
Group 4c	Active comparator	Participants will be blinded and receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: Covifenz
Group 5c	Active comparator	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. Receives: Biological: mRNA-1273 SARS-CoV-2 vaccine; Biological: BNT162b2
Group 6c	Active comparator	Participants will be blinded and receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: Covifenz
Group 7c	Experimental	Participants will receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle. Receives: Biological: Covifenz

What is being measured

The primary outcome is the main question the study is designed to answer.

Antibody response to SARS-CoV-2 S protein after 2 doses
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.
Measured: Day 56
Antibody response to SARS-CoV-2 S protein after 2 doses
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.
Measured: Day 140
Antibody response to SARS-CoV-2 S protein after 3 doses
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.
Measured: Day 28
Antibody response to SARS-CoV-2 S protein after 4 doses
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.
Measured: Day 28

Secondary outcomes (14)

Durability of antibody response to SARS-CoV-2 S over 12 months after 2 doses
Assess durability of immune responses in each study group over 12 months based on anti-spike antibody titers and pseudoneutralization assay.
Measured: Baseline and Days 28, 56, 112, 140, 365
Pseudoneutralization assay, T cell testing, Antibody dependent cellular cytotoxicity (ADCC), Antibody avidity, RNA seq after 2 doses
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.
Measured: Days 28, 56, 112, 140, 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
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).
Measured: From time of first study injection through Day 365.
Incidence of grade 3 solicited local and systemic adverse events, SAEs, AEFIs, MAAEs, AESIs in the 7 days following vaccine receipt after 3 doses
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).
Measured: From time of first study injection through Day 365.
Acceptability of vaccines as determined by participant-completed questionnaire after 2 doses
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.
Measured: Days 56, 140, and 365
Acceptability of vaccines as determined by participant-completed questionnaire after 3 doses
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.
Measured: Days 28, 180
Antibody to SARS-CoV-2 S and N, RBD after 3 doses
Assess durability of the immune responses in each study group over 12 months after the study vaccine.
Measured: Days 180 and 365
Pseudoneutralization assay, T cell testing, Antibody dependent cellular cytotoxicity after 3 doses
Further characterize the immune response to COVID-19 vaccine in schedules with homologous and heterologous third doses to day 365
Measured: 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
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).
Measured: From time of first study injection through Day 365.
Acceptability of vaccines as determined by participant-completed questionnaire after 4 doses
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).
Measured: Days 28, 180
Antibody to SARS-CoV-2 S and N, RBD after 4 doses
Assess durability of the immune responses in each study group over 12 months after the study vaccine.
Measured: Days 180 and 365
Antibody dependent cellular cytotoxicity after 4 doses
Further characterize the immune response to COVID-19 vaccine in schedules with homologous and heterologous third doses to day 365
Measured: Day 365
Pseudoneutralization assay after 4 doses
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
Measured: Day 365
T cell testing after 4 doses
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
Measured: Day 365

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

20 May 20211 Aug 2025

First posted20 May 2021
Study start20 May 2021
Primary completion15 Nov 2024
Study completion1 Aug 2025 (estimated)

Resources

Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
Other trials for COVID-19Studies of the same condition, open and under way.
What the trial phases meanHow a treatment moves from first tests in people to approval.

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design

Study type: Interventional
Phase: Phase 2
Primary purpose: Prevention
Allocation: Randomised
Intervention model: Parallel groups
Model description: M=Moderna SpikeVax mRNA; P=Pfizer/BioNTech Comirnaty mRNA; A=AstraZeneca Vaxzervia; C=Medicago Covifenz VLP MOSAIC 1: * Group 1 - M, M - 28 days * Group 2 - M, M - 112 days * Group 3 - M, P - 28 days * Group 4 - M, P - 112 days * Group 5 - P, P - 28 days * Group 6 - P, P - 112 days * Group 7 - P, M - 28 days * Group 8 - P, M - 112 days * Group 9 - A, M - 28 days * Group 10 - A, M - 112 days * Group 11 - A, P - 28 days * Group 12 - A, P - 112 days MOSAIC 2: * Group 1b - P, P, P * Group 2b - P, P, M * Group 3b - M, M, M * Group 4b - M, M, P * Group 5b - P and M in any order, M * Group 6b - P and M in any order, P * Group 7b - A, P or M, P * Group 8b - A, P or M, M * Group 9b - Any vaccine in any order, C (open-label) MOSAIC 3: * Group 1c - P, P, P, P * Group 2c - P, P, P, C * Group 3c - M, M, M, M * Group 4c - M, M, M, C * Group 5c - Any 3 in any order, P or M * Group 6c - Any 3 in any order, C * Group 7c - Any 3 in any order, C (open-label)
Masking: Triple blind
Who is masked: Participant, Investigator, Outcomes assessor
Enrolment: 669 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT04894435
Sponsor's protocol ID: CT24
Acronym: MOSAIC
Status last verified: Mar 2025
First submitted: 18 May 2021
Last updated: 18 Mar 2025
Results posted: No
Data monitoring committee: Yes
FDA-regulated drug: No
FDA-regulated device: No

Want to know more?

The sponsor has not listed a contact. The official record may have more details.

Talk to your doctor first and take this page with you. Only the study team can confirm whether you can join.

Questions to ask the study team

What is the study trying to find out?
What would I need to do, and how often would I visit?
Could I receive a placebo instead of the treatment?
What are the possible risks and benefits for me?
Will it cost me anything? Are travel or time paid for?
Can I keep seeing my own doctor during the study?
What happens when the study ends?

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Study at a glance

From the registry record, last updated by the sponsor on 18 Mar 2025. Recruitment status is as the sponsor reported it: confirm with the study team.

Official 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?
ClinicalTrials.gov ID: NCT04894435
Acronym / sponsor ID: MOSAIC / CT24
Conditions: COVID-19
Keywords: SARS-CoV-2, vaccine, clinical trial
Phase: Phase 2
Study type: Interventional
Recruitment status: Active, not recruiting
Enrolment: 669 participants (actual)
Lead sponsor: Canadian Immunization Research NetworkResearch network
Collaborators: Canadian Center for Vaccinology, BC Children's Hospital Research Institute, Children's Hospital Research Institute of Manitoba, CHU de Quebec-Universite Laval, Ottawa Hospital Research Institute, Ontario Agency for Health Protection and Promotion, University of Toronto, Massachusetts General Hospital, Interior Health, McGill University Health Centre/Research Institute of the McGill University Health Centre
Study start: 20 May 2021 (actual)
Primary completion: 15 Nov 2024 (actual)
Study completion: 1 Aug 2025 (estimated)
First posted: 20 May 2021 (actual)
Results: Not posted in the source record

Clinical summary

The research question as the sponsor registered it. This describes what the study plans to test, not what it found.

Detailed description

Study design

Primary purpose: Prevention
Allocation: Randomised
Intervention model: Parallel groups
Masking: Triple blind (participant, investigator, outcomes assessor)
Number of arms: 28
Model description: M=Moderna SpikeVax mRNA; P=Pfizer/BioNTech Comirnaty mRNA; A=AstraZeneca Vaxzervia; C=Medicago Covifenz VLP MOSAIC 1: * Group 1 - M, M - 28 days * Group 2 - M, M - 112 days * Group 3 - M, P - 28 days * Group 4 - M, P - 112 days * Group 5 - P, P - 28 days * Group 6 - P, P - 112 days * Group 7 - P, M - 28 days * Group 8 - P, M - 112 days * Group 9 - A, M - 28 days * Group 10 - A, M - 112 days * Group 11 - A, P - 28 days * Group 12 - A, P - 112 days MOSAIC 2: * Group 1b - P, P, P * Group 2b - P, P, M * Group 3b - M, M, M * Group 4b - M, M, P * Group 5b - P and M in any order, M * Group 6b - P and M in any order, P * Group 7b - A, P or M, P * Group 8b - A, P or M, M * Group 9b - Any vaccine in any order, C (open-label) MOSAIC 3: * Group 1c - P, P, P, P * Group 2c - P, P, P, C * Group 3c - M, M, M, M * Group 4c - M, M, M, C * Group 5c - Any 3 in any order, P or M * Group 6c - Any 3 in any order, C * Group 7c - Any 3 in any order, C (open-label)

Arm	Type	Receives
Group 1: Moderna, Moderna - 28 Days apart	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccine, Other: 0, 28 day scheduleParticipants 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.
Group 2: Moderna, Moderna - 112 days apart	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccine, Other: 0, 112 day scheduleParticipants 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.
Group 3: Moderna, Pfizer/BioNTech - 28 days apart	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccine, Biological: BNT162b2, Other: 0, 28 day scheduleParticipants 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.
Group 4: Moderna, Pfizer/BioNTech - 112 days apart	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccine, Biological: BNT162b2, Other: 0, 112 day scheduleParticipants 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.
Group 5: Pfizer/BioNTech, Pfizer/BioNTech - 28 days apart	Active comparator	Biological: BNT162b2, Other: 0, 28 day scheduleParticipants 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.
Group 6: Pfizer/BioNTech, Pfizer/BioNTech - 112 days apart	Active comparator	Biological: BNT162b2, Other: 0, 112 day scheduleParticipants 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.
Group 7: Pfizer/BioNTech, Moderna - 28 days apart	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccine, Biological: BNT162b2, Other: 0, 28 day scheduleParticipants 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.
Group 8: Pfizer/BioNTech, Moderna - 112 days apart	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccine, Biological: BNT162b2, Other: 0, 112 day scheduleParticipants 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.
Group 9: Astra Zeneca, Moderna - 28 days apart	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccine, Biological: ChAdOx1-S [recombinant], Other: 0, 28 day scheduleParticipants 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.
Group 10: Astra Zeneca, Moderna - 112 days apart	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccine, Biological: ChAdOx1-S [recombinant], Other: 0, 112 day scheduleParticipants 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.
Group 11: Astra Zeneca, Pfizer/BioNTech - 28 days apart	Active comparator	Biological: BNT162b2, Biological: ChAdOx1-S [recombinant], Other: 0, 28 day scheduleParticipants 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.
Group 12: Astra Zeneca, Pfizer/BioNTech - 112 days apart	Active comparator	Biological: BNT162b2, Biological: ChAdOx1-S [recombinant], Other: 0, 112 day scheduleParticipants 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.
Group 1b	Active comparator	Biological: BNT162b2Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle.
Group 2b	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccineParticipants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle.
Group 3b	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccineParticipants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle.
Group 4b	Active comparator	Biological: BNT162b2Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle.
Group 5b	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccineParticipants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle.
Group 6b	Active comparator	Biological: BNT162b2Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle.
Group 7b	Active comparator	Biological: BNT162b2Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle.
Group 8b	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccineParticipants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle.
Group 9b	Experimental	Biological: CovifenzParticipants will receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle.
Group 1c	Active comparator	Biological: BNT162b2Participants will be blinded and receive one dose (0.3mL) of BNT162b2 vaccine via intramuscular injection in the deltoid muscle.
Group 2c	Active comparator	Biological: CovifenzParticipants will be blinded and receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle.
Group 3c	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccineParticipants will be blinded and receive one half dose (0.25mL) of mRNA-1273 vaccine via intramuscular injection in the deltoid muscle.
Group 4c	Active comparator	Biological: CovifenzParticipants will be blinded and receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle.
Group 5c	Active comparator	Biological: mRNA-1273 SARS-CoV-2 vaccine, Biological: BNT162b2Participants 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.
Group 6c	Active comparator	Biological: CovifenzParticipants will be blinded and receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle.
Group 7c	Experimental	Biological: CovifenzParticipants will receive one dose (0.5mL) of Covifenz vaccine via intramuscular injection in the deltoid muscle.

Who may qualify

Ages: 18 to 99 years
Sex: All
Healthy volunteers: Accepted
Age groups: Adult, Older adult

Key inclusion criteria (8 listed)

Participant is willing and able to give written informed consent to participate in the study
Age 18 years of age or older in good health or with mild or moderate stable co-morbidities at the time of enrolment
Able and willing to complete all the scheduled study procedures during the whole study follow-up period
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)
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)

Key exclusion criteria (11 listed)

Inability or unwillingness of participant or legally acceptable representative to give written informed consent
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
Current diagnosis or treatment for cancer (except basal cell carcinoma of the skin)
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
Allergy to any study vaccine or any active substance in a study vaccine

Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.

Interventions

Intervention	Type	Arms
mRNA-1273 SARS-CoV-2 vaccineAlso: COVID-19 Vaccine Moderna, SpikevaxContains 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.	Biological	Group 10: Astra Zeneca, Moderna - 112 days apart, Group 1: Moderna, Moderna - 28 Days apart, Group 2: Moderna, Moderna - 112 days apart, Group 2b, Group 3: Moderna, Pfizer/BioNTech - 28 days apart, Group 3b, Group 3c, Group 4: Moderna, Pfizer/BioNTech - 112 days apart, Group 5b, Group 5c, Group 7: Pfizer/BioNTech, Moderna - 28 days apart, Group 8: Pfizer/BioNTech, Moderna - 112 days apart, Group 8b, Group 9: Astra Zeneca, Moderna - 28 days apart
BNT162b2Also: Pfizer-BioNTech COVID-19 Vaccine, ComirnatyA white to off-white, sterile, preservative-free, frozen suspension for intramuscular injection, supplied with 0.9% sodium chloride diluent for injection plastic ampoules.	Biological	Group 11: Astra Zeneca, Pfizer/BioNTech - 28 days apart, Group 12: Astra Zeneca, Pfizer/BioNTech - 112 days apart, Group 1b, Group 1c, Group 3: Moderna, Pfizer/BioNTech - 28 days apart, Group 4: Moderna, Pfizer/BioNTech - 112 days apart, Group 4b, Group 5: Pfizer/BioNTech, Pfizer/BioNTech - 28 days apart, Group 5c, Group 6: Pfizer/BioNTech, Pfizer/BioNTech - 112 days apart, Group 6b, Group 7: Pfizer/BioNTech, Moderna - 28 days apart, Group 7b, Group 8: Pfizer/BioNTech, Moderna - 112 days apart
ChAdOx1-S [recombinant]Also: Astra Zeneca COVID-19 Vaccine, COVISHIELD AstraZeneca COVID-19 Vaccine, VaxzevriaA colourless to slightly brown, clear to slightly opaque solution containing 5 x 1010 viral particles (not less than 2.5 x 108 infectious units).	Biological	Group 10: Astra Zeneca, Moderna - 112 days apart, Group 11: Astra Zeneca, Pfizer/BioNTech - 28 days apart, Group 12: Astra Zeneca, Pfizer/BioNTech - 112 days apart, Group 9: Astra Zeneca, Moderna - 28 days apart
0, 28 day scheduleSecond injection administered 28 days post first injection	Other	Group 11: Astra Zeneca, Pfizer/BioNTech - 28 days apart, Group 1: Moderna, Moderna - 28 Days apart, Group 3: Moderna, Pfizer/BioNTech - 28 days apart, Group 5: Pfizer/BioNTech, Pfizer/BioNTech - 28 days apart, Group 7: Pfizer/BioNTech, Moderna - 28 days apart, Group 9: Astra Zeneca, Moderna - 28 days apart
0, 112 day scheduleSecond injection administered 112 days post first injection	Other	Group 10: Astra Zeneca, Moderna - 112 days apart, Group 12: Astra Zeneca, Pfizer/BioNTech - 112 days apart, Group 2: Moderna, Moderna - 112 days apart, Group 4: Moderna, Pfizer/BioNTech - 112 days apart, Group 6: Pfizer/BioNTech, Pfizer/BioNTech - 112 days apart, Group 8: Pfizer/BioNTech, Moderna - 112 days apart
CovifenzAlso: Medicago COVID-19 vaccineCOVIFENZ 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	Biological	Group 2c, Group 4c, Group 6c, Group 7c, Group 9b

Primary outcome

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.

14 secondary outcomes

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
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
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.
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.
Acceptability of vaccines as determined by participant-completed questionnaire after 2 doses
Time frame: Days 56, 140, and 365
Acceptability of vaccines as determined by participant-completed questionnaire after 3 doses
Time frame: Days 28, 180
Antibody to SARS-CoV-2 S and N, RBD after 3 doses
Time frame: Days 180 and 365
Pseudoneutralization assay, T cell testing, Antibody dependent cellular cytotoxicity after 3 doses
Time frame: 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.
Acceptability of vaccines as determined by participant-completed questionnaire after 4 doses
Time frame: Days 28, 180
Antibody to SARS-CoV-2 S and N, RBD after 4 doses
Time frame: Days 180 and 365
Antibody dependent cellular cytotoxicity after 4 doses
Time frame: Day 365
Pseudoneutralization assay after 4 doses
Time frame: Day 365
T cell testing after 4 doses
Time frame: Day 365

Results and safety

This study is still under way. Results are not available in the source record yet.

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 18 Mar 2025.

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Referral and contact

AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.

Joanne Langley principal investigator

Dalhousie University/CIRN

8 sites in 1 country: see every site and its status.

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing mRNA-1273 SARS-CoV-2 vaccine, BNT162b2 and ChAdOx1-S [recombinant] in people with COVID-19, run by Canadian Immunization Research Network at 8 sites in Canada.

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 8 inclusion and 11 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: under way, not looking for participants, as of the sponsor's last update on 18 Mar 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 8 sites in Canada. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this phase mean?

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Antibody response to SARS-CoV-2 S protein after 2 doses (time frame: Day 56). The study lists 4 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT04894435.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 18 Mar 2025.