Journal article
Immunogenicity and safety of ChAdOx1 nCoV-19 (AZD1222) as a homologous fourth-dose booster: a substudy of the phase 3 COV003 trial in Brazil
- Abstract:
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Objective:
To address that, despite widespread use of ChAdOx1 nCoV-19 (AZD1222) as a COVID-2019 booster, fourth-dose clinical outcomes data are limited. We report immunogenicity and safety for ChAdOx1 nCoV-19 as a homologous fourth-dose booster.
Participants and Methods:
Participants (aged ≥18 years) who had received 2 doses of ChAdOx1 nCoV-19 in phase 3 COV003 trial in Brazil were offered a third dose after a planned dose interval from 11 to 13 months and a fourth dose after a planned interval from 6 to 15 months (both 5 × 1010 viral particles). All fourth doses were administered to substudy participants between August 18 and October 28, 2022. The data cutoff was December 9, 2022. The primary immunogenicity outcome was noninferiority of ancestral severe acute respiratory syndrome coronavirus (SARS-CoV)-2–neutralizing antibody responses 28 days after dose 4 versus dose 3. Solicited and unsolicited adverse events were recorded 7 and 28 days postdose 4, respectively.
Results:
172 participants received a fourth dose (median interval postthird dose, 10.7 months). Ancestral SARS-CoV-2–neutralizing antibody titers postdose 4 were noninferior to those postdose 3; geometric mean fold rise was 1.9 (95% CI, 1.6-2.4; n=112). Immunogenicity results were consistent across all variants analyzed. Local and systemic solicited adverse events were reported in 60.3% (n=35/58) and 43.1% (n=25/58) of participants, respectively. Conclusion Immune responses after a fourth dose of ChAdOx1 nCoV-19 were noninferior to those after a third dose across SARS-CoV-2 variants. The fourth dose was well tolerated with no emergent safety concerns, supporting the continued development of the ChAdOx1 platform in preparation for future pandemics.
Trial Registration:
clinicaltrials.gov Identifier: NCT04536051
- Publication status:
- Published
- Peer review status:
- Peer reviewed
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- Files:
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(Preview, Supplementary materials, pdf, 9.8MB, Terms of use)
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(Preview, Version of record, pdf, 1.4MB, Terms of use)
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- Publisher copy:
- 10.1016/j.mayocpiqo.2025.100642
Authors
Contributors
+ COV003 Study Group
- Role:
- Contributor
+ Eldawi, A
- Institution:
- University of Oxford
- Division:
- MSD
- Department:
- Paediatrics
- Role:
- Contributor
+ Sheehan, E
- Institution:
- University of Oxford
- Division:
- MSD
- Department:
- Paediatrics
- Role:
- Contributor
+ Woodlock, S
- Institution:
- University of Oxford
- Division:
- MSD
- Department:
- Paediatrics
- Role:
- Contributor
- Publisher:
- Elsevier
- Journal:
- Mayo Clinic Proceedings Innovations Quality & Outcomes More from this journal
- Volume:
- 9
- Issue:
- 4
- Article number:
- 100642
- Publication date:
- 2025-07-11
- Acceptance date:
- 2025-06-12
- DOI:
- EISSN:
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2542-4548
- Language:
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English
- Pubs id:
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2247010
- Local pid:
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pubs:2247010
- Deposit date:
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2025-07-23
- ARK identifier:
Terms of use
- Copyright holder:
- Clemens et al.
- Copyright date:
- 2025
- Rights statement:
- © 2025 The Authors. Published by Elsevier Inc on behalf of Mayo Foundation for Medical Education and Research. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
- Licence:
- CC Attribution (CC BY)
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