It is possible that later iterations of the mRNA vaccines will not require such super-cool conditions – but given the breakneck speed of development, this data on the stability of the vaccine’s chemical structure is not yet widely available.
However Moderna, who originally cited minus 70 as the temperature required within the cold chain, has already revised that figure to minus 24.
And Pfizer has announced that it will provide a bespoke ‘dry ice pack’ system for its vaccine candidate under development with BioNTech.
The packaging will be able to maintain minus 70 degrees to 10 days before vaccines require re-icing. But there is a catch: the ice will need to be replenished within 24 hours of receipt at hospitals and clinics, while the jabs will no longer work after 24 hours of refrigeration or two hours of thawing.
Coordinating the supply chain to ensure that these vaccines not only remain cold, but arrive within a time window to use them, is a daunting, costly task – especially when so many vaccines will need to be distributed at once.
However there are hopes that the majority of vaccine candidates will not need to be frozen, but can instead be stored and distributed in refrigerators at between two and eight degrees.
Protein-based immunisations, from groups including Oxford/AstraZeneca and Johnson and Johnson, are targeting this temperature range. Based on previous vaccines this is realistic, said Cepi’s Dr Jackson, but “they need to generate the data to allow that claim to be on the vaccine label”.
Any vaccine which falls between two and eight degrees is standard and can easily be absorbed into existing vaccination programmes, Gian Gandhi, Unicef’s chief of market shaping and supplier financing, told The Telegraph.
The biggest complication could be delivering the full vaccine course, he added.
“Most manufacturers have indicated that they’re targeting a two dose schedule for the vaccine.
“All of that is important because it is going to make administration more difficult, irrespective of whether we’re talking about the US, the UK or a developing country, because you need people to come back for their second dose or their booster and [you need to make] sure the cold chain infrastructure is sufficient to store double doses,” Mr Gandhi said.
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