Fig. 7: Long-term stability assessment of lyophilized vaccine formulation.

a Timeline of the stability study. Lyophilized CPVax-CoV was stored at 4 °C and 25 °C, and standard liquid vaccines were stored at −80 °C as controls. Aliquots of each condition were reconstituted at the indicated time-points to characterize their physicochemical properties and to evaluate their in vivo activity. At 0, 3, 6, and 9 months, production of specific antibodies in serum was analyzed by ELISA after a single immunization of BALB/c mice with 1 µg of mRNA/animal. At 12 months, an efficacy study was conducted. After prime-boost immunization, animals were infected with mouse-adapted SARS-CoV-2, and neutralization, viral load and cytokines in lungs were evaluated. b Determination of diameter, PDI, Z potential, and encapsulation efficacy of liquid and lyophilized LNPs at the indicated time-points of storage. c Reciprocal endpoint titers of anti-RBD IgG antibodies in serum samples collected at day 21 post-immunization were determined by ELISA after the indicated time-points of storage. d Determination of diameter, PDI, Z potential, and encapsulation efficacy at different time-points after resuspension and storage at 4 °C of CPVax-CoV. e Reciprocal endpoint titers of anti-RBD IgG antibodies in serum samples collected at day 21 post-immunization were determined by ELISA at different time-points after resuspension and storage at 4 °C of CPVax-CoV. Graphs are represented as mean ± SD. ns non-significant; as determined by one-way ANOVA with Tukey post-test. wks weeks.