Quantitative and Qualitative Evaluation of Mrna Vaccines after Sterile Filtration

Background and importance The importance of mRNA-based vaccines increased rapidly due to the COVID-19 pandemic. However, little is known on the challenges linked to handling shortages and extended stability of these new types of substance. Since vaccine remnants have to be discarded according to the Summary of Product Characteristics, we hypothesise that sterile filtration after pooling is suitable to save vaccine material for clinical application. Aim and objectives The aim of this pilot study was to compare quality parameters of remnants derived from ready-to-use mRNA vaccine solutions before and after sterile filtration. Therefore, we pooled mRNA vaccine solution remnants from Corminaty vials (BioNTech/Pfizer) and compared particle size, distribution and quantity of the lipoplexes. In addition, quantity and/or quality of the mRNA was determined. Material and methods Measurements of invisible particulates in the range 1-50 mm were performed by light obscuration according to the European Pharmacopoeia (10th edn). The size of lipoplexes was measured with nanoparticle tracking analysis (NTA) to determine hydrodynamic diameter and particle concentration. Dynamic light scattering was employed complementarily to the NTA technique to focus on particle size from 0.3 nm to 10 mm. The concentration, purity and integrity of the mRNA was analysed by ultraviolet (UV) spectrophotometry and capillary electrophoresis after mRNA purification. Results After pooling the remnants of the vials we found a substantial increase of particulates >1 mm when compared to fresh vaccine samples. This effect was likely due to contamination of the examined probes with particles from ambient air. As expected, all these particulates were eliminated by sterile filtration. Size distribution and concentration of the lipoplexes were comparable between unfiltered and filtered samples. With respect to the mRNA, we identified the fragment of interest in all examined samples. Sterile filtration did not change the concentration, purity and integrity of the mRNA. Conclusion and relevance Our results indicate that sterile filtration of mRNA-based vaccines eliminates particle contamination from the vaccine solution while the concentration of lipoplex nanoparticles was not altered. Moreover, neither the quantity nor quality of the mRNA was affected by the filtration process. The results of our pilot study provide the first data on the stability of mRNA vaccines and help to fill knowledge gap when dealing with these substances in hospital pharmacy.