Thermostable bivalent & trivalent filovirus vaccines from insect cells: potency demonstrated after 3 months and 2 years.

Filoviruses, including the well-known Ebola virus, are among the most lethal pathogens known. The current vaccine landscape is constrained by stringent cold chain requirements making vaccine deployment challenging, especially in regions with limited infrastructure. ERVEBO®, the sole FDA-approved filovirus vaccine, requires ultra-cold storage. We previously developed recombinant subunit vaccines using Drosophila S2-insect cells for protein expression, protecting non-human primates against each of the three most pathogenic filoviruses, namely Orthoebolavirus zairense, Orthoebolavirus sudanense, and Orthomarburgvirus marburgense. In the present study, we show stability (potency) of bi- and trivalent filovirus vaccine formulations comprised of protein antigens from these three viral pathogens co-lyophilized with CoVaccine HT™ in a single-vial format after extended storage at 25 °C and 40 °C. Potency was demonstrated after 3 months and 2 years using stability-indicating assays including vaccine immunogenicity in a mouse model. The lyophilized formulations remained stable and retained their potent immunogenicity for up to 2 years at both 25 °C and 40 °C, offering a promising solution for shelf-stable insect-cell derived protein vaccines suitable for easy storage and distribution even in low-resource settings.