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

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.

Timeline

Start

2022-05-27

Primary completion

2022-09-30

Completion

2024-11-06

Publications

• Background 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.
• Batmunkh 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.
• 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.
• 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.

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