The world reacted with almost universal relief when news broke on Monday that an effective Covid-19 vaccine might be imminent. But then the reality of the task dawned: what were the practicalities of immunising the world?
A massive undertaking in itself, but one made even more challenging since the Pfizer-BioNTech vaccine needs to be stored at minus 70C.
Put simply, the pharmaceutical industry is not currently configured for a “cold chain” at the low temperatures required for storage.
Dr Alexander Edwards, associate professor in biomedical technology at the University of Reading, said: “In general cold chain distribution and storage is built into the pharmaceutical supply chain – even the shelves on your corner pharmacist will have regular temperature checks. But minus 80 freezing is not routine.”
But it’s not a lost cause.
One solution is to keep the vaccine at minus 70C until the final hours is a suitcase-sized container that will keep the doses at the required temperature for up to ten days. The Times has reported that each container holds 1,000 to 5,000 doses.
“The cold chain is going to be one of the most challenging aspects of delivery of this vaccination,” said Amesh Adalja, senior scholar at Johns Hopkins Centre for Health Security in Baltimore, US.
“This will be a challenge in all settings because hospitals even in big cities do not have storage facilities for a vaccine at that ultra-low temperature.”
The necessity for this temperature of storage also poses problems surrounding the distribution of the vaccine globally.
Some low income countries face significant challenges when transporting vaccines which only need to be stored in refrigerators at 4C – let alone minus 70C.
To get to the UK, the vaccine could come from Pfizer’s distribution centre in Belgium to GP practices across Britain.
On Tuesday, health secretary Matt Hancocck said he has “confidence” the NHS can deliver an approved vaccine despite the logistics involved.
Hancock, who acknowledged the “mammoth logistical operation”, said that from the moment the vaccine leaves the factory in Belgium it can only be taken out of minus 70C four times before it is injected into a patient’s arm.
But it can be stored at a warmer temperature in the two days prior to being used, he added.
This implies that GPs will be able to administer the vaccines two days after deliveries without the need for new refrigeration systems.
But experts said the hurdles could be overcome.
Dr Simon Clarke, associate professor of cellular microbiology at the University of Reading, said on Monday: “There are production and distribution problems to be overcome, but these should not be beyond the wit of human ingenuity.”
Dr Charlie Weller, head of vaccines programme at Wellcome, told the PA news agency: “The cold chain that’s needed, that’s going to be a challenge where there are health systems and countries where that cold chain is not set up, or it is not able to be set up in a timely manner.
“So that is going to potentially mean that we need different options, we need a range of vaccines.”
The Moderna vaccine, which is working on a formula based on similar technology, does not need to be stored at such a low temperature.
Other vaccines including ones from Johnson & Johnson and Novavax can be stored at 2-8 degrees C, the temperature of a regular refrigerator.
Pfizer spokesperson Kim Bencker said one detailed plan includes using dry ice to transport frozen vaccine vials by both air and land at their recommended temperatures for up to 10 days.
They can be kept in an ultra-low temperature freezer for up to six months, or for five days at 2-8 degrees C – a type of refrigeration commonly available at hospitals, Bencker said.
The Pfizer storage units can also be refilled with ice for up to 15 days, she said.
But shots will spoil in around five days at normal refrigeration temperatures of slightly above freezing. BioNTech CEO Ugur Sahin told Reuters the companies are analyzing if they can extend that for two weeks.