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Updated: Jun 13, 2025
Protocol for Recombinant RBD-based SARS Vaccines: Protein Preparation, Animal Vaccination and Neutralization Detection
Published on: May 2, 2011
Booster vaccination using bivalent DS-5670a/b is safe and immunogenic against SARS-CoV-2 variants in children aged
Rino Suzuki1, Miharu Suda1, Katsuyasu Ishida1
1R&D Division, Daiichi Sankyo Co., Ltd., Tokyo, Japan.
Insights
The bivalent DS-5670a/b messenger ribonucleic acid (mRNA) vaccine demonstrated non-inferiority to bivalent BNT162b2 in children aged 5-11 years. This COVID-19 booster vaccine showed a manageable safety profile and broad neutralization against Omicron sublineages.
Area of Science:
- Vaccinology
- Immunology
- Virology
Background:
- DS-5670 is an mRNA vaccine platform targeting SARS-CoV-2 spike protein's receptor-binding domain (RBD).
- Previous studies show monovalent DS-5670a and bivalent DS-5670a/b are effective and safe COVID-19 boosters in adults.
- This study reports Phase 2/3 data on DS-5670a/b as a third booster dose in children.
Purpose of the Study:
- To evaluate the immunogenicity and safety of a third booster dose of bivalent DS-5670a/b.
- To compare DS-5670a/b against bivalent BNT162b2 in children aged 5-11 years.
- To assess neutralization activity against SARS-CoV-2 Omicron variants.
Main Methods:
- A Phase 2/3, active-controlled, non-inferiority study in children aged 5-11 years.
- Participants received a third booster dose of either DS-5670a/b (20 µg mRNA) or bivalent BNT162b2 (10 µg mRNA).
- Primary endpoints included neutralization geometric mean titer (GMT) against SARS-CoV-2 Omicron BA.5.2.1 and immune response rate on Day 29.
Main Results:
- Bivalent DS-5670a/b showed a GMT ratio of 1.636 (95% CI, 1.221, 2.190) compared to bivalent BNT162b2, exceeding non-inferiority margins.
- Immune response rates were ≥ 89% for both vaccines, meeting the primary endpoint.
- DS-5670a/b demonstrated broad neutralization against Omicron sublineages with no COVID-19 cases reported between Days 8-29 post-vaccination.
Conclusions:
- Bivalent DS-5670a/b is non-inferior to bivalent BNT162b2 in terms of immunogenicity for pediatric COVID-19 booster vaccination.
- The vaccine has a manageable safety profile in children aged 5-11 years.
- DS-5670a/b offers broad protection against circulating Omicron sublineages.
Background:
DS-5670 is a messenger ribonucleic acid (mRNA) vaccine platform targeting the receptor-binding domain (RBD) of the spike protein derived from severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). Booster vaccination against coronavirus disease 2019 (COVID-19) with monovalent DS-5670a (incorporating mRNA encoding the RBD from the original SARS-CoV-2 strain) or bivalent DS-5670a/b (original and omicron BA.4-5 RBD antigens) is effective and safe in adults. Data from a phase 2/3 active-controlled, non-inferiority, pediatric study evaluating a third booster dose of DS-5670a/b are reported here.
Methods:
Children aged 5-11 years who had completed the two-dose primary vaccination series with monovalent BNT162b2 (original strain) at least 3 months prior to enrolment were randomly assigned to receive DS-5670a/b (20 µg of mRNA) or bivalent BNT1 62b2 (original/omicron BA.4-5; 10 µg of mRNA) on Day 1. The primary efficacy endpoint was blood neutralization geometric mean titer (GMT) against SARS-CoV-2 (omicron variant BA.5.2.1) and immune response rate (≥ 4-fold increase in post-vaccination circulating anti-SARS-CoV-2 neutralizing activity) on Day 29.
Results:
Among evaluable participants (DS-5670a/b, n = 74; bivalent BNT162b2, n = 75), the adjusted GMT ratio of DS-5670a/b to bivalent BNT162b2 on Day 29 was 1.636 (95% CI, 1.221, 2.190). Immune response rates were ≥ 89% with both study vaccines; adjusted difference 2.6% (95% CI, -7.8, 13.8). The prespecified non-inferiority margins were exceeded, and the study met the primary endpoint. DS-5670a/b also demonstrated broad neutralization activity across recent omicron sublineages and no cases of COVID-19 between Days 8-29 post-administration were reported. There were no novel safety concerns in the pediatric population at data cut-off.
Conclusions:
Bivalent DS-5670a/b was non-inferior to bivalent BNT162b2 in terms of immunogenicity, and had a manageable safety profile, when administered as a heterologous booster in children aged 5-11 years.
Clinical Trial Registration:
https://jrct.niph.go.jp/, identifier jRCT2031220665.
