By Michaeleen Doucleff

This week the world is attempting a first — the largest, quickest rollout of a vaccine in history. The goal is to make the polio vaccine safer, but it comes with a big risk.

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Source:: http://www.npr.org/2016/04/18/474725579/new-polio-vaccine-rollout-comes-with-a-big-risk?utm_medium=RSS&utm_campaign=healthcare