Evaluation of Full Versus Fractional Dose of COVID-19 Vaccine Given as a Booster for the Prevention of COVID-19 in Adults in Mongolia.

NCT05265065 | Completed Phase 3 Results DMC FDA Drug

• 1 other identifier: 81800
• Study Type: interventional
• Target: 601
• Locations: 1 country
• Sites: 1

Brief 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 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.

Conditions

COVID-19

Keywords

Booster dose; Pfizer; fractional and standard doses; COVID-19 vaccination; mRNA vaccine

Outcome Measures

Primary Outcomes (2)

• 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.

  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.

  7 days post booster vaccination

Secondary Outcomes (17)

• Seroresponse by Priming Vaccine Strata

  28-days post booster vaccination

• SARS-CoV-2 Specific IgG Antibodies at Day-28

  28-days post booster vaccination

• SARS-CoV-2 Specific IgG Antibodies at Day-28 by Priming Vaccine Strata

  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.

  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).

  Baseline (pre-booster), 28 days, 6 months, 12 months, 18 months, and 24 months post-booster vaccination.

Study Arms (2)

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.

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.

Biological: Tozinameran - Fractional Dose

Interventions

Tozinameran - Standard Dose BIOLOGICAL

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.

Also known as: BNT162b2, Comirnaty, Pfizer Covid-19 vaccine

Standard Pfizer-BioNTech booster group

Tozinameran - Fractional Dose BIOLOGICAL

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.

Also known as: BNT162b2, Comirnaty, Pfizer Covid-19 vaccine

Fractional Pfizer-BioNTech booster group

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• 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

You may not qualify if:

• 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

Sponsors & Collaborators

• Murdoch Childrens Research Institute: lead
• Coalition for Epidemic Preparedness Innovations: collaborator
• The Peter Doherty Institute for Infection and Immunity: collaborator

Study Sites (1)

District Health Centre

Ulaanbaatar, Mongolia

Location

Related Publications (3)

• 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.

  PMID: 34863358 BACKGROUND

• Batmunkh 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.

  PMID: 41072276 DERIVED

• Batmunkh 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.

  PMID: 38357398 DERIVED

Related Links

• Quarter-dose of Moderna COVID vaccine still rouses a big immune response
• US Food and Drug Administration (FDA). Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventive Vaccine Clinical Trials 2007

MeSH Terms

Conditions

COVID-19

Interventions

BNT162 Vaccine

Condition Hierarchy (Ancestors)

Pneumonia, Viral; Pneumonia; Respiratory Tract Infections; Infections; Virus Diseases; Coronavirus Infections; Coronaviridae Infections; Nidovirales Infections; RNA Virus Infections; Lung Diseases; Respiratory Tract Diseases

Intervention Hierarchy (Ancestors)

mRNA Vaccines; Nucleic Acid-Based Vaccines; Vaccines, Synthetic; Recombinant Proteins; Proteins; Amino Acids, Peptides, and Proteins; Vaccines; Biological Products; Complex Mixtures; COVID-19 Vaccines; Viral Vaccines; Antigens; Biological Factors

Results Point of Contact

• Title: Kim Mulholland
• Organization: Murdoch Children's Research Institute

kim.mulholland@mcri.edu.au

+61 3 99366656

Study Officials

• Tsetsegsaikhan Batmunkh, MD

  Ministry of Health, Mongolia

  PRINCIPAL INVESTIGATOR

• Kim Mulholland, MD/Prof

  Murdoch Childrens Research Institute

  PRINCIPAL INVESTIGATOR

Publication Agreements

• PI is Sponsor Employee: Yes

Study Design

• Study Type: interventional
• Phase: phase 3
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Masking Details: The participants and those evaluating reactogenicity will be blinded to the vaccine allocation for the first 28 days following vaccination. After that, both clinical investigators and participants will be aware of their investigational product allocation. Laboratory staff will remain blinded to the investigational product allocation during the immunology testing.
• Purpose: PREVENTION
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: 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.

Study Record Dates

• First Submitted: March 1, 2022
• First Posted: March 3, 2022
• Study Start: May 27, 2022
• Primary Completion: September 30, 2022
• Study Completion: November 6, 2024
• Last Updated: March 24, 2026
• Results First Posted: September 19, 2024

Record last verified: 2026-03

Data Sharing

• IPD Sharing: Will share
• Shared Documents: STUDY PROTOCOL, ICF
• Time Frame: Individual participant data (IPD) sharing plans in development
• Access Criteria: IPD sharing plans in development

Locations

MO (1)