We have a covid-19 vaccine that works. But can we keep it cold enough to get it to enough people? Among Pfizer and BioNTech鈥檚 long , which this week was reported to be 90 per cent effective, is the challenge of its 鈥渦ltra-low temperature formulation鈥�, and how to store and distribute it along the so-called 鈥渃old chain鈥�.
Between manufacture and doses being given to people, the vaccine needs to be kept frozen at about -70掳C, around four times colder than a home freezer can manage. Once it has left Pfizer鈥檚 manufacturing facilities in Kalamazoo, Michigan, and Puurs, Belgium, the vaccine cannot be thawed and frozen more than four times in transit, . He said that adds 鈥渁nother tricksiness鈥� to logistics.
The vaccine, developed using a new approach of using messenger RNA from the coronavirus, is unusual in needing such low temperatures. Most vaccines are refrigerated at around 2-8掳C, rather than frozen. Even those that are frozen, such as the Varivax vaccine used against the virus that causes chickenpox, are stored at much higher temperatures than Pfizer鈥檚 one.
Advertisement
Nilay Shah at Imperial College London says healthcare systems have some experience of handling cells and samples at temperatures at around -70掳C. However, he says it is 鈥渘ot at the volumes we anticipate for vaccines鈥�.
Pfizer told New 杏吧原创 it is confident it can distribute the vaccine at such low temperatures. Vials of the vaccine will be put in purpose-built packaging about the size of an aircraft carry-on suitcase, weighing around 32 kilograms. Dry ice will be used inside to keep temperatures at -75掳C, give or take 15掳C, for up to 10 days. The dry ice (solid carbon dioxide) will be replenished along the journey. One trade body has there is enough capacity to supply that dry ice, at least in the US and Canada.
Deliveries will either be driven directly from Kalamazoo and Puurs to wherever they are being used, or flown to major hubs for onward distribution. For the UK, that will mean lorries and vans via Dover, so avoiding traffic jams that have been predicted in the event of a no-deal Brexit will be vital.
鈥淰accines are quite tricky beasts to transport,鈥� says Michael Head at the University of Southampton, UK. The easy bit will be when the vaccine is on a lorry, but it will become harder to keep the vaccine cold enough at transitions, such as when it is moved into or out of freezers at distribution centres. Shah says ultra low-temperature freezer capacity is already being scaled up at transport and warehouse hubs, but international distribution will be 鈥渕ore complex鈥�.
The delicate nature of the vaccine means that everything needs to be ready at its 鈥減oint of use鈥�, such as a doctor鈥檚 surgery. Once thawed and put in a fridge at 2-8掳C, Pfizer says it will be stable for five days, or no more than 2 hours at room temperature. Penny Ward at the Faculty of Pharmaceutical Medicine in London says careful planning is needed so that healthcare teams have patients 鈥渞eady to go鈥� at vaccination sites.
Ultimately, keeping the vaccine at the right temperature will be a logistical headache but not an insurmountable one, especially for a country like the UK, says Head. And even if there is a need for more equipment such as low temperature freezers along the supply chain, it will be possible: 鈥淚t鈥檚 such an important challenge that even if it鈥檚 expensive, cumbersome and time-consuming, it鈥檚 worth the effort to get the extra infrastructure in place.鈥�
The picture may be different in hotter countries and those lacking this infrastructure. Keeping vaccines at such low temperatures 鈥渋s extremely challenging or even impossible鈥� in low and middle-income countries with hot, humid weather, according to a 聽by the UK鈥檚 Royal Society.
One way around that may be the water-removal process of lyophilisation, turning the vaccine into a powdered form, says Ward. Pfizer says it is considering the approach. Some countries may simply opt for alternative vaccines that don鈥檛 need to be kept so cold, should they become available. 鈥�Even if the Pfizer vaccine is 90 per cent effective, we may see other countries choosing other vaccine candidates even if they鈥檙e less effective, simply because the logistics will be much easier for them,鈥� says Head.
