Vaccination is one of the biggest public health triumphs of our era, the rise of anti-vaxxers in rich countries notwithstanding. Globally, 85 percent of 1-year-olds have been vaccinated — usually for diphtheria, whooping cough, tetanus, polio, measles, and hepatitis B. That’s a huge deal; it has saved millions of lives and been one of the biggest drivers of dramatic reductions in infant mortality over the past 50 years.
But while most kids have been vaccinated, they often haven’t gotten all the vaccines they need for full immunity — only 7 percent of kids in the poorest 73 countries have all the doses of all the recommended vaccines. And one big factor that contributes to this problem is that vaccines aren’t so easily stored. They need to be kept cold, from the moment they’re manufactured to the moment they’re injected into a patient.