Formulation and stability design spaces for a new yellow fever vaccine

Yellow fever (YF) is a life-threatening disease that is entirely preventable through vaccination. The objective of this study was to formulate a freeze-dried presentation of a live-attenuated, Vero cell-based yellow fever vaccine (vYF) with improved manufacturability and enhanced shelf-life. Considering four critical quality attributes (i.e., glass transition temperatures and infectious titers at two time points), a comprehensive formulation screening was performed to identify an optimal combination of excipients, capable of protecting the virus during lyophilization while ensuring long-term stability of the vYF infectious titer. Overall, L-proline, urea, and poloxamer 407 demonstrated a stabilizing effect, and the application of an advanced kinetic model enabled prediction of a 60-month shelf-life at 5 °C for the formulated vaccine. Machine learning models were used to build both formulation and stability design spaces that defined global stabilizing regions within the explored concentration ranges of each excipient. This study demonstrates that the combination of systematic excipient screening and advanced analytics enables the selection of robust formulations with long-term stability within an accelerated development timeframe. The developed vaccine formulation has the potential for large-scale industrial production and can address substantial market demand in the coming years, representing a significant advancement in vYF technology.