© WHO/Marcel Crozet School children in New Delhi, the capital, rally in support of a nation-wide polio vaccination campaign in December 1999. That month, India vaccinates 150 million children in just a few days — the largest public health event ever undertaken. The same year, the World Health Assembly resolves to intensify the global effort and recommends adding a "door-to-door" strategy to reach every child under five. New annual cases of polio paralysis drop to 20,000.