Background and Importance COVID-19 emerged as a novel infectious disease by late 2019, spreading very rapidly and being categorised as a pandemic by March 2020 by the WHO. Several vaccines have been authorised and administered worldwide, demonstrating efficacy and safety, being Pfizer-BioNTech (Comirnaty) and Moderna (Spikevax) the mostly administered globally. Although having demonstrated efficacy and safety, one of the major issues has been their stability, from which hardly any stability data is available in the public domain. Analysing the in-use stability of these novel vaccines is paramount for ensuring rationale use in hospitals.
Aim and Objectives This study is aimed at assessing and comparing the in-use stability of Comirnaty and Spikevax clinical solutions by characterising the particulate profile using Dynamic Light Scattering (DLS).
Material and Methods Expired and non-expired clinical solutions of the vaccines were subjected to different stress conditions: visible light and mechanical stresses. The Z average and the polydispersity index (PDI) of the vaccines clinical solutions were evaluated by DLS, using a Zetasizer Nano ZS-90 (Malvern, UK). For statistical analysis, a simple ANOVA followed by Dunnett’s post-hoc test, using GraphPad Prism 8 Software was used. Stressed samples were compared to control (non-stressed samples). Furthermore, differences were considered significant at a p-value < 0.05. The study was conducted in triplicate.
Results Comirnaty DLS parameters were mainly affected by mechanical agitation and vortex stresses. In this case, the Z-average and PDI increased significantly, even in the expired samples. On the other hand, the DLS parameters were maintained in Spikevax clinical samples regardless of the stress and the expiration date.
Conclusion and Relevance This study highlights the necessity of a careful preparation of these vaccines, given their demonstrated fragility upon gentle stress. However, Comirnaty has proven to be more fragile than Spikevax in their handling in real-use conditions. Previous literature commented on the stability of Comirnaty, having presented similar results. Nonetheless, no stability data were available on the in-use stability of Spikevax. Therefore, this data will be of interest to hospital pharmacists towards following vaccination campaigns.
Acknowledgements To the Farmacy Unit from the San Cecilio Clinical University Hospital (Granada, Spain) to support and facilitate this investigation.
Conflict of Interest No conflict of interest
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