The final battle against polio?

There’s no one place a virus goes to die — but that doesn’t make its demise any less a public health victory. Throughout human history, viral diseases have had their way with us, and for just as long, we have hunted them down and done our best to wipe them out. In the developed world, vaccines have made once-common scourges such as measles, rubella, mumps and whooping cough rare to the point of near-extinction. Only once, however, has any virus been flushed from its last redoubts in both the body and the wild and effectively vaccinated out of existence. That virus was smallpox, which ceased to exist outside high-security labs in 1977. Since that day, humanity has been free to put the vaccines against the disease — and the terror its periodic outbreaks would cause — on the shelf forever. Now we are tantalizingly close to another such epic moment. This...