The world is about to make a risky move to eradicate polio for good

Public health workers and scientists are on the brink of eradicating polio, a disease that causes incurable paralysis. But total eradication calls for a massive logistical operation “unprecedented” in the history of vaccines: In the next weeks, 155 countries and territories will safely dispose of hundreds of millions of polio vaccines, switching to a new version of the vaccine. The goal of the switch is to stop immunizing against Type 2 polio. Since this strain of the virus was eradicated in 1999, the Type 2 component of the oral polio vaccine is no longer needed, according to polio experts. The new vaccine will immunize only against Types 1 and 3. If the switch is successful, it will dramatically reduce the incidence of vaccine-associated polio. Polio vaccines are simply weakened strains of the virus. In very rare circumstances — 1 in a million vaccines — the weakened polio virus present in the vaccine mutates...