International Externalities in Pandemic Influenza Mitigation

Abstract

A serious influenza pandemic could be devastating for the world. Ideally, such a pandemic could be contained, but this may be infeasible. One promising method for pandemic mitigation is to treat infectious individuals with antiviral pharmaceuticals. While most of the benefits from treatment accrue to the country in which treatment occurs, there are some positive spillovers: when one country treats more of its population this both reduces the attack rate in the other country and increases the marginal benefit from additional treatment in the other country. These externalities and complementarities may mean that self-interested rich countries should optimally pay for some AV treatment in poor countries.

This dissertation demonstrates the presence of antiviral treatment externalities in simple epidemiological SIR models, and then in a descriptively realistic Global Epidemiological Model (GEM). This GEM simulates pandemic spread between cities through the international airline network, and between cities and rural areas through ground transport.

Under the base case assumptions of moderate transmissibility of the flu, the distribution of antiviral stockpiles from rich countries to poor and lower middle income countries may indeed pay for itself: providing a stockpile equal to 1% of the population of poor countries will reduce cases in rich countries after 1 year by about 6.13 million cases at a cost of 4.62 doses per rich-country case avoided. Concentrating doses on the outbreak country is, however, even more cost-effective: in the base case it reduces the number of influenza cases by 4.76 million cases, at the cost of roughly 1.92 doses per case avoided. These results depend on the transmissibility of the flu strain, the efficacy of antivirals in reducing infection and on the proportion of infectious who can realistically be identified and treated.