The Question

Considering both epidemiological and economic concerns, what is the optimum level of control of immunizing infections? How does this vary on a local and global scale for weakly and strongly coupled populations?

What we found

The economic optimum is to tolerate some cases of less serious infections, especially if vaccination costs are high.

Why it matters

The results show that the strength of coupling between populations has important consequences for incentives of local decision makers. Focusing on local budgetary limitations, we find the present value of infecteds is so high in short-term cost-effective strategies that the cost of current infections outweighs the benefit of preventing cases in the future. Long-term optimal strategies, onthe other hand, stress the value of herd immunity to the extent that it might make sense for a patch to spend on vaccination in another patch rather than its own.