How dry ice shortages can complicate Pfizer vaccine deliveries
Pfizer #Pfizer
In what is the largest vaccine donation by a single country, U.S. President Joe Biden’s administration announced last week plans to buy 500 million doses of Pfizer’s COVID-19 vaccine and donate them to more than 90 lower-income countries and the African Union. This will include 200 million doses this year and 300 million doses next year.
Until recently, the Pfizer vaccine was not considered as an ideal candidate for low-resource settings because of its need for storage in ultracold temperatures between minus 80 degrees Celsius and minus 60 C. Only 27 of the 131 countries that received vaccines from the COVAX have received doses of the Pfizer vaccine.
In May, the U.S. Food & Drug Administration and South Africa’s regulator authorized the storage of undiluted, thawed vials of the vaccine for up to one month at refrigerator temperatures — which was welcome news to the global health community. But not all countries have adopted these new refrigerator storage requirements.
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Even with these changes in storage requirements, the capacity to store and move this vaccine in low-resource settings still poses challenges. Though Pfizer’s specialized ultracold thermal shipping container may provide a short-term storage solution for such settings, health experts warn that access to dry ice may provide yet another limitation.
Limited access to dry ice
Pfizer ships the vaccines in a specialized ultracold thermal shipping container that requires dry ice to maintain ultracold temperatures.
When a country receives shipments of vaccines in Pfizer’s specialized container, there are three options for storage. It can put them in an ultracold temperature freezer, which will allow for a shelf life of six months — the Africa Centres for Disease Control and Prevention says these freezers will cost countries around $15,000. Or it can store the vaccine at the normal refrigeration temperature of 2 C-8 C for one month.
Countries can also use Pfizer’s specialized ultracold thermal shipping container which can be refilled with dry ice every 5 days, for up to 30 days. After storage for 30 days in Pfizer’s thermal shipper, the vaccines can be transferred to 2 C-8 C storage conditions for an additional five days.
Because of this option, these containers could be used as a cold chain solution in areas without access to cold chain systems — or in areas where the cold chain has already reached storage capacity, said Caitlin Burton, the vice president of global health partnerships at Zipline.
But dry ice is a difficult substance to make and is not produced on a wide scale in some countries, said Stefano Marani, CEO at the South Africa-based company Renergen, a helium and domestic natural gas producer. And the production of dry ice consumes a lot of electricity, making it expensive, he said.
“It is a commodity that is quite tricky to produce and quite tricky to handle. It’s also insanely heavy,” Marani said, adding that the cost of moving dry ice to remote areas for the purpose of distributing vaccines is prohibitively expensive in many settings.
These limitations on dry ice can also limit how many vaccines a country can bring in at a time, Burton said. If there is not an adequate supply of dry ice, a country will need to quickly transfer vaccines that have arrived to refrigerators or freezers. This means they would need space in a cold chain system that could be near capacity.
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“There’s actually a lot of careful planning that needs to go in upfront about when you will import a shipment, when it needs to be transferred out of its box into a freezer,” Burton said.
Undiluted vials of the Pfizer vaccine can be stored at room temperature for no more than two hours after thawing, and vials must be fully utilized within six hours after the first dose is extracted, at room temperature. The vaccines cannot be refrozen once thawed, according to a Pfizer spokesperson.
Another issue with dry ice is shipping by air, Marani said. When dry ice is used to fly vaccines from a manufacturing plant to a country, there is a limit on the quantity of dry ice that can be on a plane. Dry ice is a solid version of carbon dioxide and in too high of quantities, it can displace air and lead people to asphyxiate on a plane.
“Right now the world uses dry ice to move vaccines around, which is a massively inefficient system,” he said.
Finding solutions
Renergen has developed an alternative transport method to using dry ice that uses a helium-powered freezer called Cryo-Vacc, which would allow for more doses to be transported by plane. Marani said that with dry ice, about 40,000 vaccine doses can be transported in a single aircraft, while this solution can carry about 3.6 million doses.
He also said Cryo-Vacc can be used as a freezer for ground transportation of vaccines to remote areas. It can stay cold for 30 days, as opposed to the Pfizer containers that need to be replenished with dry ice every 5 days. When countries have a shorter time frame to distribute these doses, they need more health workers to quickly distribute the vaccines — in a race against the clock, he said, adding that in some settings it’s not possible to have a surge in the supply of health workers. The company plans to be involved in the vaccine roll out in South Africa in the coming weeks.
Zipline and Pfizer have also been working on developing a cold chain solution that can keep the doses of any cold-chain-dependent vaccine cold while they are in drones. This is to get vaccines out quickly and equitably to populations, with the idea to “liberate access to doses beyond the cold chain,” Burton said.
Drones would transport the vaccines across countries, including in remote parts of countries. The vaccines would then need to be used that day if a health clinic does not have access to cold chain facilities, she said. This helps in getting the vaccine to priority groups outside of urban areas.
“If a country is going to receive a bunch of doses at once, chances are they need to utilize all of the capacity in their cold chain to store it,” Burton said. “It’s important to roll these doses out as quickly as possible.”
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