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Lookup NU author(s): Dr Stephen Owens
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
Copyright © 2025 The Author(s). Published by Elsevier Ltd. All rights reserved. BACKGROUND: The emergence of SARS-CoV2 variants combined with waning vaccine-induced immunity and breakthrough infections has highlighted the need for booster doses to maintain protection against SARS-CoV2 infection and disease. METHODS: Com-COV3 was a phase II, multicentre, randomised controlled trial, recruiting across 11 UK sites from June 2022 to June 2023, with follow-up visits to February 2024. Healthy 12-15-year-olds who had received a two-30 μg dose BNT162b2 primary regimen at least 90 days previously were randomised 1:1:1:1:1 to receive either BNT162b2 30 μg, BNT162b2 10 μg (adult vaccine formulation), BNT162b2 10 μg (paediatric formulation), NVXCoV2373, or Meningococcal B vaccine (control). The primary objective was to determine if SARS-CoV-2 anti-spike antibody following a 10 μg dose of the adult formulation of BNT162b2 was non-inferior to the paediatric formulation at 28 days post-third vaccination. The last five participants were randomised using a 1:3:3:1:1 ratio to prioritise recruitment to the study groups required for the co-primary endpoint. Although recruitment ceased early, the sample size required to fulfil the primary objective was met. FINDINGS: 281 participants were recruited (mean age 14 years old, 57% female). Adverse reactions were mostly mild-to-moderate. Local reactogenicity was mildest following NVXCoV2373. Frequency of adverse events was similar for both full dose and fractional dose BNT162b2 groups. Four serious adverse events occurred: three in the paediatric and one in the adult 10 μg BNT162b2 group. Immunogenicity of 10 μg BNT162b2 (adult) was both non-inferior and superior to that of 10 μg BNT162b2 (paediatric); adjusted geometric mean ratio (aGMR) anti-spike IgG 1.50 (one-sided 95% CI 1.25 to ∞). Compared with 30 μg BNT162b2, anti-spike IgG at day 28 post-third dose were similar in the 10 μg BNT162b2 (adult) group [aGMR 0.93 (95% CI 0.75-1.14)] and significantly lower in the 10 μg BNT162b2 (paediatric) [aGMR 0.64 (95% CI 0.52-0.78)] and NVXCoV2373 [aGMR 0.77 (95% CI 0.63-0.95)] groups. Compared with 30 μg BNT162b2, levels of neutralising antibodies against Omicron BA.5 and XBB.15 were similar across vaccine groups. INTERPRETATION: All booster regimens evaluated elicited a robust immune response. 10 μg fractional adult BNT162b2 vaccine demonstrated similar immunogenicity compared with 30 μg BNT162b2 and superior immunogenicity compared with 10 μg paediatric BNT162b2 vaccine. Fractional doses of the adult BNT162b2 vaccine are an alternative to the paediatric formulation for booster campaigns in adolescents.
Author(s): Kelly E, Greenland M, de Whalley P, Macaulay GC, Aley PK, Plested E, Koleva S, Cotton J, Kinch J, Madupuri T, Read RC, Ramsay M, Cameron C, Turner DPJ, Heath P, Connor P, Cathie K, Faust SN, Banerjee I, Man K, Shackley F, O'Riordan S, Owens S, Polychronakis T, Trari Belhadef H, Mujadidi Y, Singha A, Cantrell L, Clutterbuck E, Anslow R, James T, Hallis B, Matheson M, Chang L, Lambe T, Nguyen-Van-Tam JS, Snape MD, Minassian AM, Liu X
Publication type: Article
Publication status: Published
Journal: Journal of Infection
Year: 2026
Volume: 92
Issue: 1
Print publication date: 01/01/2026
Online publication date: 01/12/2025
Acceptance date: 28/11/2025
Date deposited: 26/01/2026
ISSN (print): 0163-4453
ISSN (electronic): 1532-2742
Publisher: Elsevier Ltd
URL: https://doi.org/10.1016/j.jinf.2025.106663
DOI: 10.1016/j.jinf.2025.106663
Data Access Statement: The study protocol is provided in the Supplement. Individual participant data will be made available when the trial is complete, upon requests directed to the corresponding author; after approval of a proposal, data can be shared through a secure online platform.
PubMed id: 41338394
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