Mass vaccination was the tried-and-true approach to smallpox eradication. Mass vaccination success was measured by the percentage of the population that was vaccinated, in order to achieve herd immunity. Most countries, WHO and other multilateral organizations were committed to this approach and operationally tied the goals to this strategic approach.

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.

In 1973 India had thousands of cases of smallpox. For a while they were reporting one thousand new cases every day. Leaders of the eradication effort wanted to solicit help from WHO and bring in physicians, epidemiologists and health worker volunteers from other countries to supplement the Indian teams. But the Minister of Health for India felt that India had plenty of health workers and volunteers to do the job and said that people from other countries were not needed. The Minister's support for the smallpox effort was essential, so the team had to convince him to support bringing in workers from other countries without being critical of the great resources India already had.