In the early 1960s, India accounted for nearly 60 percent of the reported smallpox cases in the world. The Indian government had launched the National Smallpox Eradication Program which focused on mass vaccination. By 1966, the Indian government reported approximately 60 million primary vaccinations. Mass vaccination campaigns had become part of the culture, and there was wide trust in this singular approach. However, the number of smallpox cases in India was increasing and India needed a new strategy.

An effective vaccine for preventing smallpox had been discovered and tested by 1796. And by the 1970’s widespread vaccination resulted in most people in rich countries being vaccinated and almost completely protected. Smallpox was actually eliminated from developed countries in the 1970s. But the burden of smallpox was inequitably distributed. People in some poor countries remained vulnerable and faced high risks of mortality from smallpox. It was within the poorest communities that smallpox was spread.