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Volume 13
Issue 2
10.3390/vaccines13020169
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Article

Efficacy of Inactivated Bivalent SARS-CoV-2 Vaccines Targeting Ancestral Strain (ERAGEM), Delta, and Omicron Variants

by
Busra Kaplan
1,
Shaikh Terkis Islam Pavel
1,
Muhammet Ali Uygut
1,
Merve Tunc
1,
Yesari Eroksuz
2,
Ilhami Celik
3,
Esma Eryilmaz Eren
4,
Gulay Korukluoglu
5,
Ates Kara
6,
Aykut Ozdarendeli
1,7 and
Hazel Yetiskin
1,*
1
Vaccine Research and Development Institute, Erciyes University, 38280 Kayseri, Türkiye
2
Department of Pathology, Faculty of Veterinary Medicine, Fırat University, 23100 Elazig, Türkiye
3
Department of Infectious Disease and Clinical Microbiology, University of Health Sciences, 38080 Kayseri, Türkiye
4
Department of Infectious Diseases and Clinical Microbiology, Kayseri City Education and Research Hospital, 38080 Kayseri, Türkiye
5
Department of Clinical Microbiology, University of Health Sciences, Ankara Bilkent City Hospital, 06800 Ankara, Türkiye
6
Pediatric Infectious Department, Faculty of Medicine, Hacettepe University Hospitals, 06230 Ankara, Türkiye
7
Department of Medical Microbiology, Faculty of Medicine, Erciyes University, 38280 Kayseri, Türkiye
*
Author to whom correspondence should be addressed.
Vaccines 2025, 13(2), 169; https://doi.org/10.3390/vaccines13020169
Submission received: 3 January 2025 / Revised: 28 January 2025 / Accepted: 4 February 2025 / Published: 10 February 2025
(This article belongs to the Section COVID-19 Vaccines and Vaccination)
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Abstract

Background/Objectives: The rapid evolution of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to the emergence of variants with enhanced transmissibility and immune evasion, challenging existing vaccines. This study aimed to evaluate the immunogenicity and protective efficacy of inactivated bivalent vaccine formulations incorporating the ancestral SARS-CoV-2 strain (ERAGEM) with either Delta or Omicron (BA.5) variants. Methods: Bivalent vaccine formulations were prepared using beta-propiolactone-inactivated SARS-CoV-2 antigens and administered to K18-hACE2 transgenic mice. Following prime and booster immunizations, neutralizing antibody titers and viral loads were assessed through ELISA, microneutralization assays, and quantitative PCR. Mice were challenged with the respective variants, and the survival rates, temperature, and body weight changes were monitored for 21 days. Results: Both vaccine formulations elicited significant increases in neutralizing antibody titers post-booster immunization. The ERAGEM + Delta group demonstrated geometric mean titers (GMTs) of 6938.1 and 4935.0 for the ancestral and Delta variants, respectively, while the ERAGEM + Omicron (BA.5) group achieved GMTs of 16,280.7 and 24,215.9 for the ancestral and Omicron (BA.5) variants. Complete survival (100%) was observed in all the vaccinated groups post-challenge, with no detectable viral titers in the lungs and substantial reductions in the nasal turbinate viral loads compared to the unvaccinated controls. Conclusions: The bivalent inactivated vaccines demonstrated strong immunogenicity and complete protection against severe disease in preclinical models. These findings indicate the potential of bivalent vaccine strategies in addressing antigenic diversity and preparing for future pandemics caused by rapidly evolving pathogens.
Keywords: SARS-CoV-2; bivalent vaccine; inactivated vaccine; immune response; pandemic preparedness SARS-CoV-2; bivalent vaccine; inactivated vaccine; immune response; pandemic preparedness

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MDPI and ACS Style

Kaplan, B.; Pavel, S.T.I.; Uygut, M.A.; Tunc, M.; Eroksuz, Y.; Celik, I.; Eren, E.E.; Korukluoglu, G.; Kara, A.; Ozdarendeli, A.; et al. Efficacy of Inactivated Bivalent SARS-CoV-2 Vaccines Targeting Ancestral Strain (ERAGEM), Delta, and Omicron Variants. Vaccines 2025, 13, 169. https://doi.org/10.3390/vaccines13020169

AMA Style

Kaplan B, Pavel STI, Uygut MA, Tunc M, Eroksuz Y, Celik I, Eren EE, Korukluoglu G, Kara A, Ozdarendeli A, et al. Efficacy of Inactivated Bivalent SARS-CoV-2 Vaccines Targeting Ancestral Strain (ERAGEM), Delta, and Omicron Variants. Vaccines. 2025; 13(2):169. https://doi.org/10.3390/vaccines13020169

Chicago/Turabian Style

Kaplan, Busra, Shaikh Terkis Islam Pavel, Muhammet Ali Uygut, Merve Tunc, Yesari Eroksuz, Ilhami Celik, Esma Eryilmaz Eren, Gulay Korukluoglu, Ates Kara, Aykut Ozdarendeli, and et al. 2025. "Efficacy of Inactivated Bivalent SARS-CoV-2 Vaccines Targeting Ancestral Strain (ERAGEM), Delta, and Omicron Variants" Vaccines 13, no. 2: 169. https://doi.org/10.3390/vaccines13020169

APA Style

Kaplan, B., Pavel, S. T. I., Uygut, M. A., Tunc, M., Eroksuz, Y., Celik, I., Eren, E. E., Korukluoglu, G., Kara, A., Ozdarendeli, A., & Yetiskin, H. (2025). Efficacy of Inactivated Bivalent SARS-CoV-2 Vaccines Targeting Ancestral Strain (ERAGEM), Delta, and Omicron Variants. Vaccines, 13(2), 169. https://doi.org/10.3390/vaccines13020169

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