Smallpox eradication in West and Central Africa: surveillance-containment or herd immunity?

The global eradication of smallpox stands among the most important public health achievements of the last century. However, fears that smallpox bioweapons have fallen into the hands of rogue states or terrorist organizations have rekindled interest in the methods used to control smallpox outbreaks. Surveillance-containment employing ring vaccination, whereby symptomatic smallpox cases were sought and isolated and their surrounding contacts traced and vaccinated, has been widely acknowledged as the key to smallpox eradication, though some have questioned this claim. In the United States, where the interim policy in the event of a smallpox attack is based on ring vaccination, we have argued that localized mass vaccination from the moment an attack is recognized would result in far fewer casualties than ring vaccination, including deaths that result from vaccination itself. In this commentary, we closely examine a figure based on historical data reported by Foege et al documenting smallpox control and eradication in West and Central Africa. This figure has been resurrected as empirical proof of the effectiveness of ring vaccination, and presented in important meetings addressing smallpox response policy in the United States. It is important that data offered to garner support for a policy position stand on their own as presented, and indeed it was the public presentation of this figure that prompted our investigation. Contrary to