The world's now scrambling for dry ice. It's just one headache in getting coronavirus vaccines where they need to go

Vaccines like to be kept cool, none more so than the Pfizer candidate for Covid-19, which has to be deep-frozen. And that's going to be an issue for developing countries -- and for rural areas in the developed world. The 'cold chain' is just one of the challenges in distributing vaccines worldwide. There are plenty of others: decisions about priority populations and databases to keep track of who's received what vaccine, where and when. Additionally, different vaccines may have more or less efficacy with different population groups; and governments will need PR campaigns to persuade people that vaccines are safe.