Integrated Analytical Techniques to Investigate the Effect of the Freezing/Thawing Cycles on the Non-Replicating Recombinant Chimpanzee Adenovirus Viral Vector Covid-19 Vaccine

The chimpanzee adenovirus-vectored vaccine developed by the University of Oxford (ChAdOx1 nCoV-19) was one of the frontrunners in the vaccination campaign to fight the COVID-19 pandemic. Still, data regarding the stability of the vaccine after exposure to repeated freezing processes have not been explored yet. In the present study, different batches were exposed to 3 repeated freezing/thawing cycles. The tested samples were assessed in comparison with control samples for appearance, pH, and molecular size distribution by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), Anion-exchange chromatography (AEC) for determination of viable particles, and DNA to-protein ratio, in addition to In-vivo immunological test. Our results exhibited that the tested vaccines were within the release specifications for almost all the tests. Although some degradations were observed in AEC results compared to control samples, there was no in-vivo potency decrease in the tested vaccines. These findings imply that the vaccine could withstand limited freezing or thawing cycles during transportation without significant loss in its structural integrity and biological potency.