Dr Graham Rogers unpacks the critical role that vacuum technology plays in the production, storage and transport of COVID-19 vaccines.
The COVID-19 pandemic has thrust vaccines into the spotlight — and the public is increasingly interested in how vaccines are manufactured, stored and transported. This article explores how vacuum technology has made COVID-19 vaccines possible through each step of this process. We start by looking at how vacuum is used in purifying vaccines.
1. VACCINE PURIFICATION
Purification within the vaccine manufacturing process is paramount and an ultra-high-speed centrifuge is employed to facilitate this step. The different settling coefficients or buoyancy density of the components within the mixture allows the purification process to be achieved.
High rotational speeds of more than 30,000 RPM are required to produce complete separation of the active species and unwanted contaminants. Such large rotational speeds cause air friction within the mixture and result in heat generation. This can damage the active components. To counter this, high vacuum pump systems that incorporate a turbomolecular pump (TMP), and ideally a dry vacuum pump, are used to extract heat from the mixture.
2. FREEZE-drying and storing vaccines
Active microorganisms and enzymes are the key components in vaccines. Freeze-drying is employed to ensure that these components are protected and that the vaccine remains effective.
The freeze drying process involves mixing the finished live vaccine with a water-based stabiliser to form a suspension, which is then frozen. A vacuum is then applied with a little heat so that the ice sublimes from solid to vapour. Because of the low temperature of the sublimation process, the components of the vaccine remain active and undamaged.
The freeze-dried vaccine can then be sealed and stored under vacuum — this has the advantages of offering a long shelf life, rapid dissolution with diluent during use, and unchanged recovery characteristics. Vacuum storage is currently the most common method of preservation of live vaccines.
3. Vaccine glass vial production
Before transportation and distribution, the vaccine is dispensed into glass vials. The correct choice of glass is crucial to maintain the efficacy of the vaccine — only low borosilicate glass has the required chemical stability needed for long-term vaccine preservation. In addition, this glass has excellent stability to thermal expansion and contraction, which is important for storage at below-ambient temperatures.
Vacuum is required in two stages of the production of borosilicate vials:
- Vacuum is used during the melting process to remove air trapped in the glass and typically operates at around 50 mbar pressure. Glass dust and high temperatures are issues that must also be addressed. Traditionally liquid ring pumps have been used. But increasingly both oil rotary vane and screw pumps are employed to reduce running costs. Dry screw pumps offer an oil-free alternative.
- The moulding process requires vacuum levels of around 100mbar. Short pump downtimes and continuous operation are key. Oil rotary vane, screw pumps and dry screw pumps are increasingly used.
4. Vaccine transportation and storage
Vacuum Insulation Panel (VIP) technology is critical to transporting COVID-19 vaccines. For example, the Pfizer BioNTech vaccine requires storage at -60°C. Maintaining this temperature presents a significant challenge.
VIPs offer a method to maintain these temperatures in an energy-efficient way. VIP offers very low thermal conductivity of 0.004W (m.K), with a typical container wall thickness of 25–60mm. By comparison, conventional mineral wool of 150mm thickness would have a value of 0.04W (m.K).
This leads to greater efficiency and more storage within the refrigeration unit.
The structure of VIP comprises three parts: insulating material, a gas adsorption material (Getter) and a closed insulating film (barrier). This closed insulating barrier is pumped to a high vacuum level before sealing, thus offering exceptional insulation properties.
The high-speed fore vacuum pumping train minimises the time before the diffusion pump kicks in, to give a rapid turnaround of the panels.
How vacuum makes COVID-19 vaccines possible
In this blog post, we’ve shown how integral vacuum technology is to the production, storage and transport of COVID-19 vaccines. Here’s a summary of what we’ve unpacked:
- The use of a high vacuum pumping system in conjunction with an Ultra-High-Speed centrifuge allows vaccine purification while minimising any detrimental effect of heat on vaccine effectiveness.
- Vacuum freeze-drying offers long-term bulk storage before transfer to dispensing vials.
- Vial production is dependent on vacuum for air removal in the melting process. Additionally, vacuum is key to moulding the uniform moulding of the vials.
- Vacuum Insulating Panel technology gives reliable and energy-efficient low temperatures that are crucial to the long-term stability of some vaccines.
From the COVID-19 vaccine to the surgery room, did you know that vacuum technology saves lives across the medical industry?
Download our free guide to learn how vacuum technology has shaped medicine.