‘The switch’ was supposed to be a major step toward eradicating polio. Now it’s a quandary

Three years ago, the leaders of the international campaign to eradicate polio pulled off a landmark feat, phasing out a problematic component of the vaccine used in developing countries, and introducing a newer version that they hoped would put the world on a better footing to finally eliminate a global scourge.

Now, some organizers are weighing whether “the switch,” as the process was known, needs to be reversed.

If it’s not, some fear, the world could face a heightened risk of spread of the disease, currently confined to its last redoubt, Pakistan and Afghanistan.

“We’re having those conversations, but we haven’t concluded anything,” said Michel Zaffran, director of polio eradication at the World Health Organization, when asked about the possibility the polio program may have to resume routine vaccination of children against type 2 polioviruses.

The decision to reverse the switch would be a devastating blow to the Global Polio Eradication Initiative, which is already nearly 20 years past its original deadline. The campaign and other polio experts stress that no decision has been made, but acknowledge that the vaccine could be returned to routine use again for a period, at least in some countries or regions.

“At this point I think I’m hesitant to switch [back],” said Dr. Walter Orenstein, a consultant for the Global Polio Eradication Initiative. “But I think that’s certainly in discussion and is a potential.”

The goal of the switch was to remove from circulation the part of the vaccine that protected