Abstract
Despite the success of current COVID-19 vaccines, the immunity they generate wanes over time, requiring periodic boosters. The limited durability of memory responses, particularly from mRNA vaccines, remains a major challenge for achieving long-term protection. Developing vaccines that induce more sustained immunity would lessen the need for frequent revaccination, improving global vaccination logistics, especially in resource-limited settings. DNA-launched self-amplifying RNA replicons (DREP) and modified vaccinia virus Ankara (MVA) vectors are promising vaccine platforms capable of inducing potent humoral and cellular immunity. In this study, we evaluated SARS-CoV-2-specific immune responses in C57BL/6 mice following homologous and heterologous prime/boost regimens combining DREP- and MVA-based vaccines expressing the spike (S) protein from either the ancestral Wuhan strain or the Omicron XBB.1.5 variant. Homologous (DREP/DREP, MVA/MVA) and heterologous (DREP/MVA) regimens were followed for six months. MVA-S(3P)-based boosters elicited robust and durable anti-S IgG antibodies cross-recognizing multiple variants, with minimal decay over time. Neutralization mapped to the booster antigen: MVA-S(3PWuhan) induced neutralization of the ancestral strain, while MVA-S(3PXBB.1.5) selectively neutralized Omicron subvariants, maintaining high titers for at least six months. MVA-S(3P) boosters also enhanced antibody Fc-effector functions, memory B cells, and T follicular helper responses. Early after boosting, heterologous DREP/MVA regimens induced stronger CD4⁺ and CD8⁺ T-cell responses, while at six months all MVA-S(3P)-boosted groups maintained superior, long-lived cellular immunity. Collectively, MVA-S(3P)-based boosters improved the magnitude, breadth, and durability of humoral and cellular responses, supporting their strategic use in homologous and heterologous DREP/MVA vaccination regimens against SARS-CoV-2 and emerging variants.
Data availability
The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.
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Acknowledgements
We thank CSIC and MCIU for continuous support. The SARS-CoV-2 MAD6 isolate was kindly provided by Dr. José M. Honrubia and Prof. Luis Enjuanes (CNB-CSIC, Madrid, Spain). The SARS-CoV-2 Beta (B.1.351) variant was obtained through the European Virus Archive goes Global (EVAg) platform under an MTA agreement. The SARS-CoV-2 Omicron BA.1 (B.1.1.529) variant was kindly provided by Prof. Piet Maes (KU Leuven, Belgium) through Dr. Robbert Boudewijns and Dr. Kai Dallmeier (KU Leuven, Belgium). The SARS-CoV-2 Omicron BA.5 (EPI_ISL_13424827), XBB.1.5 (EPI_ISL_16939528), and XBB.1.16 (EPI_ISL_17535655) subvariants were kindly provided by Prof. Rafael Delgado (Hospital Universitario 12 de Octubre, Madrid, Spain). We are also grateful to José María Casasnovas (CNB-CSIC) for providing the S proteins used in ELISAs and antibody Fc-function assays, and Jorge Esteban for managing help.
Funding
Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This work was supported by CSIC grant 202120E079, grant CNS2022-135511 funded by the Spanish Ministry of Science, Innovation and Universities (MCIU)/Spanish Research Agency (AEI)/https://doi.org/10.13039/501100011033 and by the European Union NextGenerationEU/PRTR to promote research consolidation, as well as funds from the Centro de Investigación Biomédica en Red de Enfermedades Infecciosas (CIBERINFEC) co-financed with FEDER funds (to JG-A). Additional support was provided by CSIC grant 2020E84 (to ME), and by Spanish MCIU/AEI/https://doi.org/10.13039/501100011033 grant PID2020-114481RB-I00 (to JG-A and ME). This research work also received funding from the European Commission-NextGenerationEU, through CSIC’s Global Health Platform (PTI Salud Global) (to JG-A and ME). JG-A received further funding from the European Commission HORIZON-HLTH-2023-DISEASE-03-18 (Project MARVAX: 101137183 and Project FLAVIVACCINE: 101137006). JG-A and ME also acknowledge financial support from the Spanish AEI/https://doi.org/10.13039/501100011033 through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2017-0712, CEX2023-001386-S). The funders were not involved in the study design, collection, analysis, interpretation of data, the writing of this article, or the decision to submit it for publication.
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Conceptualization: JG-A, ME, PL, GMM. Formal analysis: PP, GE, JG-A. Funding acquisition: JG-A, ME. Investigation: PP, GE, MAN, JG-A. Methodology: PP, GE, MAN, JG-A. Resources: LPV. Supervision: JG-A, ME, PL, GMM. Validation: PP, GE, ME, JG-A. Visualization: PP, GE, ME, JG-A. Writing—original draft: PP, GE, JG-A. Writing—review and editing: all authors. All authors have read and agreed to the published version of the manuscript.
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Pérez, P., Esteso, G., Noriega, M.A. et al. Homologous MVA and heterologous DREP/MVA vaccine regimens induce robust and durable immune responses against SARS-CoV-2. Sci Rep (2026). https://doi.org/10.1038/s41598-026-46699-0
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DOI: https://doi.org/10.1038/s41598-026-46699-0
