Yellow fever outbreaks are not uncommon. But, as with other infectious diseases, when they occur in urban areas, they can play out very differently - not least in terms of the speed and scale at which they can spread.
If you want to know the value of vaccines, just spend some time in a clinic in Africa. The faces of the mothers and fathers say it all: vaccines prevent illness and save lives.
The GAVI Alliance has achieved many things in its first dozen years, but none more important than helping save more than 5.5 million lives and prevent untold illness and suffering.
As more and more people adopt an urban lifestyle and cities continue to swell, not only does the risk of urban epidemics increase - something we haven't seen much of for decades - but the need for larger emergency stockpiles can increase, too.
No country in the post-colonial era has thrived without first building its capacity to conduct scientific research.
I wish we could have state-of-the-art hospitals in every corner of the earth... but realistically, it's going to be a while before that can happen. But we can immunise every kid on earth, and we can prevent these diseases. It's only a matter of political will, a little bit of money and some systems to do it.
