A brief excerpt from the wonderful book by Atul Gawande Better: A Surgeon’s Notes on Perfomance, which details a WHO led effort to try to prevent the spread of polio in southern India when a case was detected there in 2003. The plan referred to was designed to cover an area of 50,000 square miles:

The plan, he said, was to employ  thirty-seven thousand vaccinators and four thousand healthcare supervisors, rent two thousand vehicles, supply more than eighteen thousand insulated vaccine carriers, and have the works go door to door to vaccinate 4.2 million children. In three days.

This is in a section of the booked entitled Diligence. Why? For the reason that the challenge facing the team of 37,000 was that they had to reach at least 90% of the target population, children under 5 years of age, or risk the failure of the entire ‘mop up’ operation.