Editor’s Note: The Bill and Melinda Gates Foundation and other global health leaders recently launched a new effort to eradicate polio. Below, Scott Barrett comments on the potential rewards and the risks of this new initiative, and in another post Judith Kaufmann offers her thoughts on the new initiative as well.

The global effort to eradicate polio is making another push, this time with the spirited support of Bill Gates, who has made polio eradication his foundation’s number one priority.

Eradicating a disease is an audacious goal. It is also unlike any other effort, for it requires the active and enthusiastic participation of every country—indeed, of every community within every country. There is nothing like an eradication effort to bring the world together. If polio eradication succeeds, international cooperation will have been given a shot in the arm.

But eradication is a gamble. It may not succeed, despite the best efforts of a great many people. That is what is so frustrating about this goal. Success promises a prize—no future disease, and no need to vaccinate—but getting close offers no consolation. In his annual letter on his foundation’s work, released just a few days ago, Bill Gates says that one benefit of eradication is that “success will energize the field of global health by showing that investments in health lead to amazing victories.” It will. But what would failure do to the field of global health?

It is hard to aim so high and at the same time to consider the possibility of failure. It is tempting to say, “Failure is not an option.” But suppose success isn’t feasible?  We know it is theoretically feasible to reduce the number of cases worldwide to zero, because polio has been eliminated in most parts of the world and wild type 2 poliovirus has been eradicated (that is, it has been eliminated everywhere). But is eradication of the other two polioviruses practically feasible? We still don’t know.

We’ll know if we succeed. If we don’t succeed, however, we won’t know that polio can’t be eradicated. There will remain the chance that if we try a different strategy, use a different tool, deploy more resources, and get lucky, polio will be eradicated. This is one reason why it is so difficult to pull the plug on polio. This, I think, is one reason why Bill Gates is giving the program his support.

The eradication effort was begun in 1988 and was supposed to be completed by 2000. It wasn’t. Indeed, while the number of polio cases fell dramatically from the start of the initiative, the number has changed very little since 2000, varying between about 500 and 2000 every year. In his annual letter, Bill Gates confessed, “In 2003 I would have said we were just a couple of years away from ending polio, and I would have been wrong.” What, then, is different about today?

One difference is that we now have new tools, including new vaccines, thanks to efforts by the Global Polio Eradication Initiative to innovate its way around numerous obstacles. Also, the money we spent on polio eradication in the past is irrelevant to the decision of whether to push ahead. So in many ways the case for eradication is stronger today. However, over the last decade we have learned that eradication is much harder than we thought initially.

Clearly, the effort cannot go on indefinitely. At some point, if success continues to elude us, we will have to stop. There are three ways in which this could happen.

First, there could be a crisis, as when vaccination was halted in Northern Nigeria in late 2003. This local disruption meant that eradication had no chance, and funding for the initiative immediately dried up. The Global Polio Eradication Initiative was able to turn things around, but we can’t be sure it would be able to do so again if another crisis erupted in the future.

Second, financial support could fizzle out. For eradication to remain viable, funding must continue at a high level. But the willingness to contribute depends on expectations for the program’s success. Should some contributors doubt the feasibility of eradication, funding will be cut back. Funding is especially fragile as meeting each year’s budget depends on the total contribution. A donor that cuts back could not be blamed entirely for the program’s collapse. The blame would be shared, making it easier for supporters to cut back.

Third, there could be a planned transition towards a program for achieving a different goal. This would be a goal of “control.” What does this alternative look like? Critics of eradication have suggested limiting the number of cases to 500 per year, which is utterly unrealistic. For all its efforts, the eradication effort hasn’t been able to sustain a case count this low. It is inconceivable that a control program would be this successful. If the goal of eradication is abandoned, the number of cases will rise well above this level.

How high? Bruce Aylward, director of the Global Polio Eradication Initiative, said in a newspaper interview that the number of cases could jump to 250,000 per year. No one would want to plan for an outcome like that, but if the world is unwilling to finance eradication, it certainly won’t finance a control program that limits the number of cases worldwide to a very low number. The incentives wouldn’t be there.

This could be another reason why the push for eradication continues. The alternative is unclear and any realistic assessment would be too awful to contemplate.