COVID-19Phase 3NCT05265065
Evaluation of Full Versus Fractional Dose of COVID-19 Vaccine Given as a Booster for the Prevention of COVID-19 in Adults in Mongolia.
A Phase 3 study testing Tozinameran - Standard Dose and Tozinameran - Fractional Dose in people with COVID-19, run by Murdoch Childrens Research Institute at 1 site in Mongolia.
Trial summary
This clinical trial is a single-blind, randomised study to determine the reactogenicity and immunogenicity of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) vaccine (Pfizer-BioNTech) as booster dose in adults, who have previously received either Sinopharm (BBIBP-CorV®), AstraZeneca (ChAdOx1-S, or… Read more about this study
- Who is it for?
- Ages 18 years and olderHealthy volunteers can take part
- Conditions the study is for
- COVID-19
- What is being tested?
- Tozinameran - Standard Dose and Tozinameran - Fractional Dose
- Type of treatment
- Vaccines, Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 601 participants
- Where
- 1 siteMongolia
- Study dates
- 27 May 2022to 6 Nov 2024
- Phase
- Phase 3
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 years and older
- All sexes
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Have completed two doses of Sinopharm, AstraZeneca or Sputnik vaccines with the recommended schedule 6 months prior to the date of enrolment
- Willing and able to give written informed consent
- Aged 18 years or above
- Willing to complete the follow-up requirements of the study
Who cannot join
- Received 3 doses of COVID-19 vaccine
- Received 2 doses of COVID-19 less than 6 months prior to the start of the trial
- Currently on immunosuppressive medication or anti-cancer chemotherapy
- HIV infection
- Congenital immune deficiency syndrome
- Has received immunoglobulin or other blood products in the 3 months prior to vaccination
- Study staff and their relatives
- Have a history of a severe allergic reaction to any COVID-19 vaccines or have a medical exception to receiving further COVID-19 vaccines
Trial locations and contacts
1 site in 1 country.
About this study
Official title: A Randomised Controlled Trial to Assess the Immunogenicity, Safety and Reactogenicity of Standard Dose Versus Fractional Doses of COVID-19 Vaccine (Pfizer-BioNTech) Given as a Booster Dose After Priming With Sinopharm, AstraZeneca or Sputnik in Healthy Adults in Mongolia
This clinical trial is a single-blind, randomised study to determine the reactogenicity and immunogenicity of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) vaccine (Pfizer-BioNTech) as booster dose in adults, who have previously received either Sinopharm (BBIBP-CorV®), AstraZeneca (ChAdOx1-S, or Vaxzevria®) or Sputnik V (Gam-COVID-Vac®) as their primary doses 6 to 9 months earlier. Both standard and fractional doses will be tested.
Participants are healthy adults aged 18 years or older, with no upper age limit. Procedures will be implemented to ensure participants of all ages (aged 18 and above) are included and that there is an even age distribution (<50 and ≥50 years) in each group. There will be a total of 6 groups (Sinopharm-standard dose Pfizer, Sinopharm-fractional dose Pfizer, AstraZeneca-standard dose Pfizer, AstraZeneca-fractional dose Pfizer, Sputnik - standard dose Pfizer, Sputnik - fractional dose Pfizer), with 200 participants per group for Sinopharm and 100 for AstraZeneca and Sputnik.
Read the detailed description
As per brief summary
- Conditions
- COVID-19
- Being tested
- Tozinameran - Standard Dose, Tozinameran - Fractional Dose
- Keywords
- Booster dose, Pfizer, fractional and standard doses, COVID-19 vaccination, mRNA vaccine
- Medical subject headings
- COVID-19
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Tozinameran - Standard DoseBiological
Also called BNT162b2, Comirnaty, Pfizer Covid-19 vaccine
Tozinameran is a single-stranded, 5'-capped messenger RNA (mRNA) produced using a cellfree in vitro transcription from the corresponding DNA templates, encoding the viral spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
Dose - 30 µg in 0.3 ml. Liquid for injection. Single dose.
Tozinameran - Fractional DoseBiological
Also called BNT162b2, Comirnaty, Pfizer Covid-19 vaccine
Tozinameran is a single-stranded, 5'-capped messenger RNA (mRNA) produced using a cellfree in vitro transcription from the corresponding DNA templates, encoding the viral spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
Dose - 15 µg in 0.15 ml. Liquid for injection. Single dose.
| Study group | Role | What they receive |
|---|---|---|
| Standard Pfizer-BioNTech booster group | Active comparator | Biological/Vaccine: Tozinameran - Standard Dose
Other Names:
BNT162b2 Comirnaty Pfizer Covid-19 vaccine
Tozinameran is a single-stranded, 5'-capped messenger RNA (mRNA) produced using a cellfree in vitro transcription from the corresponding DNA templates, encoding the viral spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
Dose - 30 µg in 0.3 ml. Liquid for injection. Single dose. Receives: Biological: Tozinameran - Standard Dose |
| Fractional Pfizer-BioNTech booster group | Experimental | Biological/Vaccine: Tozinameran - Standard Dose
Other Names:
BNT162b2 Comirnaty Pfizer Covid-19 vaccine
Tozinameran is a single-stranded, 5'-capped messenger RNA (mRNA) produced using a cellfree in vitro transcription from the corresponding DNA templates, encoding the viral spike (S) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
Dose - 15 µg in 0.3 ml. Liquid for injection. Single dose. Receives: Biological: Tozinameran - Fractional Dose |
What is being measured
The primary outcome is the main question the study is designed to answer.
Seroresponse
Serum samples collected at 28-days post booster vaccination from all groups will be evaluated for SARS-CoV-2 specific IgG antibodies using IgG ELISA. The primary endpoint is the seroresponse rate at the Day-28 visit. The seroresponse rate at the individual level is defined as either a ≥4-fold rise in binding antibodies at the Day-28 visit compared to baseline (pre-vaccination) with a titre of <200 BAU/ml, a ≥2-fold rise among participants with a baseline (pre-vaccination) titre of >200 BAU/ml, or a ≥4-times the lower limit of detection if baseline levels are lower than the limit of detection.
Measured: 28-days post booster vaccination
Solicited Grade 3 or 4 Local or Systemic Reaction
Questionnaire to document solicited reactions is developed specifically for this study. Data will be reported as the proportion of participants who report grade 3 or 4 reactions by each intervention arm. Solicited reactions such as pain, tenderness, erythema/redness, induration, swelling, fever, nausea, vomiting, headache, fatigue/malaise, myalgia, arthralgia, diarrhea, enlarged lymph nodes will be collected from the participants 7 days post-vaccination.
Measured: 7 days post booster vaccination
Secondary outcomes (17)
Seroresponse by Priming Vaccine Strata
Serum samples collected at 28-days post booster vaccination from all groups will be evaluated for SARS-CoV-2 specific IgG antibodies using IgG ELISA. The primary endpoint is the seroresponse rate at the Day-28 visit. The seroresponse rate at the individual level is defined as either a ≥4-fold rise in binding antibodies at the Day-28 visit compared to baseline (pre-vaccination) with a titre of <200 BAU/ml, a ≥2-fold rise among participants with a baseline (pre-vaccination) titre of >200 BAU/ml, or a ≥4-times the lower limit of detection if baseline levels are lower than the limit of detection.
Priming strata (previously COVID vaccination): AstraZeneca (ChAdOx1-S, or Vaxzevria®); Sinopharm (BBIBP-CorV®); Sputnik V (Gam-COVID-Vac®)
Measured: 28-days post booster vaccination
SARS-CoV-2 Specific IgG Antibodies at Day-28
Serum samples collected at 28-days post booster vaccination from all groups will be evaluated for SARS-CoV-2 specific IgG antibodies using IgG ELISA.
Measured: 28-days post booster vaccination
SARS-CoV-2 Specific IgG Antibodies at Day-28 by Priming Vaccine Strata
Serum samples collected at 28-days post booster vaccination from all groups will be evaluated for SARS-CoV-2 specific IgG antibodies using IgG ELISA.
Priming strata (previously COVID vaccination): AstraZeneca (ChAdOx1-S, or Vaxzevria®); Sinopharm (BBIBP-CorV®); Sputnik V (Gam-COVID-Vac®)
Measured: 28-days post booster vaccination
SARS-CoV-2 Specific IgG Antibodies at Baseline (Pre-booster), 28 Days, 6 Months, 12 Months, 18 Months, and 24 Months Post-booster Vaccination.
Serum samples collected at baseline (pre booster), 28 days, 6 months, 12 months, 18 months, and 24 months post booster vaccination from the study arms will be evaluated for SARS-CoV-2 specific IgG antibodies using the commercial Euroimmun S1 IgG ELISA. Data will be reported as binding antibody units (BAU)/mL and presented as geometric mean concentration (GMC) and 95% confidence intervals (CI).
Measured: Baseline (pre booster), 28 days, 6 months, 12 months, 18 months, and 24 months post-booster vaccination.
SARS-CoV-2 Specific Neutralising Antibodies at Baseline (Pre-booster), 28 Days, 6 Months, 12 Months, 18 Months, and 24 Months Post-booster Vaccination Measured by Surrogate Virus Neutralisation Test (sVNT).
Serum samples collected at baseline (pre booster), 28 days-, 6- and 12-months post booster vaccination from all groups will be evaluated for SARS-CoV-2 specific neutralising antibodies using the GenScript® cPass surrogate virus neutralization test (sVNT) for both wild-type and Omicron variant. Neutralising antibody response will be reported as percentage (%) inhibition of receptor binding domain-angiotensin-converting enzyme 2 (RBD-ACE2) binding relative to a positive control.
Measured: Baseline (pre-booster), 28 days, 6 months, 12 months, 18 months, and 24 months post-booster vaccination.
SARS-CoV-2 Specific Neutralising Antibodies at Baseline (Pre Booster), 28 Days-, 6- and 12-months Post Booster Vaccination Measured by SARS-CoV-2 Microneutralisation Assay
A subset of samples (20%) from all four timepoints will be assessed using a SARS-CoV-2 microneutralisation assay to both the wild type (vaccine) strain and for two SARS-CoV-2 Variants of concern. Neutralizing antibody will be reported as endpoint titre.
Measured: Baseline (pre booster), 28 days-, 6- and 12-months post booster vaccination
Interferon Gamma (IFNγ) Concentrations in International Units (IU)/mL
IFN-γ concentrations (IU/mL) as a measure of cellular immunity will be assessed in a subset of participants. IFN-γ production will be stimulated using QuantiFERON Human IFN-γ SARS-CoV-2 (Qiagen) and quantified by ELISA. Results are summarised as geometric mean concentrations (GMCs) with 95% confidence intervals.
Measured: Baseline (pre booster), 28 days, 6-, 12 -, 18-, and 24-months post booster vaccination
Number of IFNγ Producing Cells/Million PBMCs
Applicable to the subset participants with additional blood collection. IFNγ producing cells as a measurement of cellular immunity will be assessed on a subset of the participants (40%) from each group. IFN-γ Enzyme-Linked ImmunoSpot (Elispot) assay will be performed on isolated peripheral blood mononuclear cells (PBMCs). Data will be reported as number of IFNγ producing cells/million and presented using means and 95% CI.
Measured: Baseline (pre-booster), 28 days, 6 and 12 months post booster vaccination
Frequency of Cytokine-expressing T Cells
Frequency of wild-type SARS-CoV-2 spike-specific cytokine-expressing T cells will be assessed in a subset of participants (~40%) using intracellular cytokine staining (ICS) by flow cytometry on PBMC samples. Results are reported as the frequency (%) of cytokine-expressing CD4 and CD8 memory T cells, summarised as geometric mean concentrations (GMCs) with 95% confidence intervals.
Measured: Baseline (pre-booster), 28 days, 6 and 12 months post-booster vaccination
Cellular Immunity: Multiplex Cytokine Assays - Reported as Cytokine Concentrations in pg/ml and Presented as GMC and 95% CI
Wild-type SARS-CoV-2 spike-specific cytokine concentrations following PBMC stimulation will be assessed in a predefined subset of participants (approximately 40%) using multiplex cytokine assays. Cytokine concentrations will be reported in pg/mL and summarised as geometric mean concentrations (GMCs) with 95% confidence intervals. IFN-γ ELISpot, intracellular cytokine staining (flow cytometry), and multiplex cytokine assays will be performed on isolated peripheral blood mononuclear cells (PBMCs).
Measured: Baseline (pre booster), 28 days-, 6 and 12 months post booster vaccination
Incidence of Unsolicited Adverse Events (AE)
All unsolicited AE will be collected for 28 days post booster vaccination. Data will be presented as proportion of participants who report unsolicited AE.
Measured: 28 days-post booster vaccination
Incidence of Medically Attended Adverse Events
All participants with medically attended AE will be collected for 3 months post booster vaccination. Data will be presented as number of participants who report unsolicited AE.
Measured: 3 months post booster vaccination
Incidence of Serious Adverse Events (SAE)
SAE will be collected throughout the follow-up period of 24 months post booster vaccination. Data will be presented as a proportion of participants who report unsolicited SAE.
Measured: 24 months post-booster
Incidence of PCR Confirmed COVID-19 Infection
Confirmed SARS-CoV-2 infections will be documented throughout the follow-up period, by clinical severity.
Measured: Up to 24 months post booster vaccination
Number of IFNγ Producing Cells/Million PBMCs
Applicable to the subset participants with additional blood collection. IFNγ producing cells as a measurement of cellular immunity will be assessed on a subset of the participants (40%) from each group. IFN-γ Enzyme-Linked ImmunoSpot (Elispot) assay will be performed on isolated peripheral blood mononuclear cells (PBMCs). Data will be reported as number of IFNγ producing cells/million and presented using means and 95% CI.
Measured: At 18 and 24 months post booster vaccination
Frequency of Cytokine-expressing T Cells
Frequency of wild-type SARS-CoV-2 spike-specific cytokine-expressing T cells will be assessed in a subset of participants (~40%) using intracellular cytokine staining (ICS) by flow cytometry on PBMC samples. Results are reported as the frequency (%) of cytokine-expressing CD4 and CD8 memory T cells, summarised as geometric mean concentrations (GMCs) with 95% confidence intervals.
Measured: 18 and 24 months post-booster vaccination
Cellular Immunity: Multiplex Cytokine Assays - Reported as Cytokine Concentrations in pg/ml and Presented as GMC and 95% CI
Wild-type SARS-CoV-2 spike-specific cytokine concentrations following PBMC stimulation will be assessed in a predefined subset of participants (approximately 40%) using multiplex cytokine assays. Cytokine concentrations will be reported in pg/mL and summarised as geometric mean concentrations (GMCs) with 95% confidence intervals. IFN-γ ELISpot, intracellular cytokine staining (flow cytometry), and multiplex cytokine assays will be performed on isolated peripheral blood mononuclear cells (PBMCs).
Measured: 18 and 24 months post booster vaccination
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted3 Mar 2022
- Study start27 May 2022
- Primary completion30 Sep 2022
- Study completion6 Nov 2024
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
- Publications (4)Papers the sponsor has linked to this study.
- 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 3
- Primary purpose
- Prevention
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- Study participants who have received two doses of either Sinopharm, AstraZeneca or Sputnik vaccine as their primary vaccine will be randomised into one of two groups. The two groups consist of a standard or fractional dose of Pfizer vaccine.
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 601 participants (actual)
Sponsor and investigators
- Lead sponsor
- Murdoch Childrens Research Institute
- Sponsor type
- University, hospital or other
- Collaborators
- Coalition for Epidemic Preparedness Innovations, The Peter Doherty Institute for Infection and Immunity
- Responsible party
- Sponsor
- Investigators
- Tsetsegsaikhan Batmunkh, MD, Principal investigator, Ministry of Health, MongoliaKim Mulholland, MD/Prof, Principal investigator, Murdoch Childrens Research Institute
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT05265065
- Sponsor's protocol ID
- 81800
- Status last verified
- Mar 2026
- First submitted
- 1 Mar 2022
- Last updated
- 24 Mar 2026
- Results posted
- Yes, on ClinicalTrials.gov
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- Yes: We will share de-identified data to ethically approved studies in cases where participants have indicated on the consent form that they consent to the use of their data and where consistent with terms of collaboration agreements.
Publications
Munro APS, Janani L, Cornelius V, Aley PK, Babbage G, Baxter D, Bula M, Cathie K, Chatterjee K, Dodd K, Enever Y, Gokani K, Goodman AL, Green CA, Harndahl L, Haughney J, Hicks A, van der Klaauw AA, Kwok J, Lambe T, Libri V, Llewelyn MJ, McGregor AC, Minassian AM, Moore P, Mughal M, Mujadidi YF, Murira J, Osanlou O, Osanlou R, Owens DR, Pacurar M, Palfreeman A, Pan D, Rampling T, Regan K, Saich S, Salkeld J, Saralaya D, Sharma S, Sheridan R, Sturdy A, Thomson EC, Todd S, Twelves C, Read RC, Charlton S, Hallis B, Ramsay M, Andrews N, Nguyen-Van-Tam JS, Snape MD, Liu X, Faust SN; COV-BOOST study group. Safety and immunogenicity of seven COVID-19 vaccines as a third dose (booster) following two doses of ChAdOx1 nCov-19 or BNT162b2 in the UK (COV-BOOST): a blinded, multicentre, randomised, controlled, phase 2 trial. Lancet. 2021 Dec 18;398(10318):2258-2276. doi: 10.1016/S0140-6736(21)02717-3. Epub 2021 Dec 2.
PubMed 34863358Batmunkh T, Neal EF, Amraa O, Mazarakis N, Altangerel B, Avaa N, Batbayar L, Batsukh K, Bright K, Burentogtokh T, Do LAH, Dorj G, Hart JD, Jamiyandorj O, Javkhlantugs K, Jigjidsuren S, Justice F, Li S, Mashbaatar K, Moore KA, Namjil N, Nguyen CD, Ochirbat B, Surenjav U, Thomson H, Tsolmon B, Licciardi PV, von Mollendorf C, Mulholland K. Fractional BNT162b2 boosters induce durable immune responses after non-mRNA priming in Mongolia: a randomised controlled trial. Front Immunol. 2026 Mar 23;17:1789248. doi: 10.3389/fimmu.2026.1789248. eCollection 2026.
PubMed 41948336Batmunkh T, Neal EFG, Amraa O, Mazarakis N, Altangerel B, Avaa N, Batbayar L, Batsukh K, Bright K, Burentogtokh T, Do LAH, Dorj G, Hart JD, Jamiyandorj O, Javkhlantugs K, Jigjidsuren S, Justice F, Li S, Mashbaatar K, Moore KA, Namjil N, Nguyen CD, Ochirbat B, Surenjav U, Thomson H, Tsolmon B, Licciardi PV, von Mollendorf C, Mulholland K. Immunogenicity and safety at twelve months of fractional and standard BNT162b2 booster doses in adults primed with ChAdOx1-S, BBIBP-CorV, or Gam-COVID-Vac in Mongolia: a randomised controlled trial. Vaccine. 2025 Nov 14;66:127840. doi: 10.1016/j.vaccine.2025.127840. Epub 2025 Oct 9.
PubMed 41072276Batmunkh T, Moore KA, Thomson H, Altangerel B, Amraa O, Avaa N, Batbayar L, Batsukh K, Bright K, Burentogtokh T, Ha Do LA, Dorj G, Hart JD, Javkhlantugs K, Jigjidsuren S, Justice F, Li S, Licciardi PV, Mashbaatar K, Mazarakis N, Neal EFG, Nguyen CD, Ochirbat B, Tsolmon B, Tuya A, Surenjav U, von Mollendorf C, Mulholland K. Immunogenicity, safety, and reactogenicity of a half- versus full-dose BNT162b2 (Pfizer-BioNTech) booster following a two-dose ChAdOx1 nCoV-19, BBIBP-CorV, or Gam-COVID-Vac priming schedule in Mongolia: a randomised, controlled, non-inferiority trial. Lancet Reg Health West Pac. 2023 Nov 21;42:100953. doi: 10.1016/j.lanwpc.2023.100953. eCollection 2024 Jan.
PubMed 38357398