On February 13, 2012, India crossed a threshold that few had believed possible a decade earlier: the country marked one full year without a single recorded case of polio. The World Health Organization removed India from its list of polio-endemic countries. A disease that had paralyzed hundreds of thousands of Indian children every year had been stopped.

The achievement was the result of one of the largest and most sustained public health campaigns in history. At its peak, India's polio eradication effort deployed more than two million vaccinators and health workers who fanned out across the country on National Immunization Days, reaching into remote villages, urban slums, high-risk migrant populations, and communities that had historically resisted vaccination.

The scientific tool was the oral polio vaccine — inexpensive, easy to administer, and highly effective. The logistical challenge was reaching every child under five in a country of more than a billion people, including populations without reliable addresses or consistent healthcare contact. This required house-to-house campaigns, transit point vaccination at railway stations and bus stops, and sustained engagement with religious and community leaders in areas where vaccine hesitancy was highest.

India's success was particularly striking given that the country had been considered one of the most difficult environments for polio eradication — dense, populous, with inadequate sanitation in many areas and significant vaccine skepticism in some communities. The strategies developed to reach the hardest-to-reach children in Uttar Pradesh and Bihar became models that informed eradication campaigns in Pakistan, Afghanistan, and Nigeria.

The celebration was warranted. So was the vigilance: maintaining polio-free status requires ongoing surveillance and vaccination, indefinitely.