Developing a COVID-19 vaccine is an immense achievement. Distributing it will be too. Jubilation greeted the better than expected trial results of the jab made by Pfizer and BioNTech last week. But the ultra-cold temperatures needed to store it caused trepidation.

Not that minus 70C is an exceptionally low temperature by medical standards. Sperm banks use liquid nitrogen – with a boiling point of minus 196C – for storage. So do cryonics facilities that, controversially, store corpses in the hope of a future medical breakthrough. Only by going below minus 136C, the temperature at which water solidifies without forming damaging ice crystals, is it possible to keep cell structures intact.