Certain sterile pharmaceutical products require deep cold storage, either at dry ice (-80°C) or even cryogenic (−196 °C) temperatures. Live viral vaccines, gene therapies, or products that contain active cells (cell therapies) often need deep cold storage to maintain stability and/or activity. These storage conditions pose a challenge to packaging components, in particular to vial/rubber stopper combinations traditionally used to fill sterile pharmaceutical product. Rubber formulations typically have glass transition temperatures (Tg’s) near -65°C meaning that rubber stoppers lose their elasticity at deep cold storage temperatures. This loss of elasticity, coupled with inappropriate capping & crimping, can result in increased risk that the vial seal integrity could be compromised. It is therefore imperative that data is generated to demonstrate the maintenance of seal integrity during deep cold storage and transport..