Coronavirus: the cold, hard challenge of delivering vaccines
- Doses of two leading candidates in the race to develop a Covid-19 vaccine must be stored in low temperatures in the longer term
- It’s a big issue in countries with cold-chain infrastructure – let alone in places beyond those supply lines
In the last week, two front-runners in the vaccine race reported promising interim results from clinical trials. Both potential vaccines rely on a new technology that is easier to mass produce but comes with a downside – the doses must be kept at low temperatures for long-term storage.
The World Health Organization (WHO) plans to produce at least 2 billion doses of coronavirus vaccine by the end of 2021. And bilateral or advance purchase agreements amount to almost 8 billion doses.
Given the scale of demand and the kind of vaccine, exceptional efforts could be needed to get the doses to all corners of the globe, according to Leonora Lim, vice-president of life sciences and healthcare at DHL Customer Solutions and Innovation, Asia-Pacific.
DHL estimates that 200,000 pallet shipments, 15 million cool-box deliveries and 15,000 cargo flights will be required to transport the billions of doses needed around the world.
“With some of the Covid-19 vaccines expected to be transported at ultra-low temperatures, we may require extraordinary measures to reach people outside about 25 countries with the most advanced logistics systems, which are home to just one-third of the world’s population,” Lim said.
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The logistics of production and delivery have come into sharper focus this month with positive news about the efficacy of two vaccine candidates.
Both the Pfizer-BioNTech and Moderna candidates use a novel technology that involves messenger protein RNA of the coronavirus but the vaccine needs to be stored at cold temperatures over the long term to stabilise the RNA against degradation.
The Pfizer-BioNTech candidate needs to be kept at -70 degrees Celsius (-94 Fahrenheit) for long-term storage. The Moderna vaccine must stay at -20 degrees Celsius (-4 Fahrenheit) if kept for 60 days and 2-8 degrees for 30 days. It can be kept for 12 hours at room temperature.
Lim said those requirements would be difficult to meet for many countries.
“Currently, large parts of Africa, South America and Asia could not be readily supported at scale due to lack of cold-chain logistics capacity suitable for life science products,” she said.
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That is in part because most vaccines are usually transported at 2-8 degrees Celsius (36-46 Farhrenheit). It is possible to handle products at ultra-low temperatures but very difficult to do so on such a large scale.
Deep cold transport would involve dry ice: frozen carbon dioxide that remains solid at temperatures below -78.48 degrees Celsius (-109 Fahrenheit) but changes to a gas that can be harmful when the temperature rises. This will affect the amount of dry ice allowed on cargo planes and limit the amount of vaccine in each shipment.
According to Project Sunrays – a collaboration between the International Air Cargo Association and Pharma.Aero to ensure Covid-19 vaccines are safely handled, stored and transported – using dry ice comes with risks.
“A very high amount of dry ice in the aircraft would impose safety risks to the aircrew. There is a limitation to the amount of dry ice that each aircraft would be able to carry,” it said.
To ensure that vaccines remained effective throughout their storage and transport, there must be adequate access to an established network of warehouses, the ability to distribute on the ground and a robust delivery network to cope with the staggering volume of shipments, Lim added.
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BioNTech CEO Ugur Sahin said the transport challenge was manageable.
Even though the company’s vaccine needed to be kept at -70 degrees Celsius for longer-term storage, it could survive five days in an ordinary refrigerator.
“We are still collecting data to see if it can be stored stably in the refrigerator for a longer time period. I don’t think transportation would be a big issue,” Sahin said.
“We believe in our collaboration with Fosun Pharma, our Chinese partner who has an extensive network for supply chain and logistics. We cooperate with Pfizer in the United States, Europe and other regions, who owns a global logistics network and supply chain.”
In the US, Pfizer has designed a special shipping box that can maintain the necessary temperature, with the doses to be shipped from its plants to points of vaccination.
In China, Fosun Pharma has built a warehouse for deep-freeze storage near an airport in Shanghai and is in talks with the drug regulator to determine if it can build a factory for local production, according to company chairman Wu Yifang.
The stringent requirements for deep freezing will be in place for at least at the beginning of the global delivery process as a precaution to keep the Covid-19 vaccines stable due to a lack of safety data.
Lim, from DHL, said the requirement might be lifted over time if tests showed the vaccine remained effective at higher temperatures or an improved formula and manufacturing came online.
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Nevertheless, the high demand on logistic infrastructure will put the vaccines out of reach for some countries, according to Professor Nikolai Petrovsky, a vaccine researcher at Flinders University in Adelaide, Australia, who is also leading a team in Australia to develop a Covid-19 vaccine.
“Definitely the issues of RNA vaccine instability will make them unsuitable for most countries other than the US and Europe,” Petrovsky said.
Even if countries choose more conventional vaccines – such as a DNA, virus-vectored or inactivated vaccine, which are generally stored at 2-8 degrees Celsius – transport for distribution at normal temperature may still be a challenge, and not only for the developing world, according to Petrovsky.
“Refrigeration and the cold chain for vaccines is a big issue, particularly in the developing world. But even in the developed world, we have many failures of the cold chain that result in vaccines being destroyed. So this is a problem worldwide even when a vaccine is stable at refrigerated temperatures,” he said.
Lim from DHL said cold-chain logistics was “always a challenge, regardless of distance”, and having robust processes, trained personnel and proper facilities and equipment in place, among other preparations, were important to reach temperature integrity for shipments.
Project Sunrays said the last mile delivery of temperature-sensitive vaccines was one of the biggest challenges in delivery.
“International organisations, NGOs and donors are called in action to support cool chain capacity-building efforts in least developed countries to ensure no one is left behind in the upcoming global immunisation campaign,” it said.
