How did mass vaccination campaigns eliminate indigenous polio from the Western Hemisphere?

The elimination of indigenous polio from the Western Hemisphere was achieved through a combination of national immunization efforts and a coordinated regional initiative. Following the successful deployment of the Salk and Sabin vaccines in countries like the United States, Canada, Cuba, and Brazil, the Pan American Health Organization (PAHO) launched a formal initiative in 1985 to eradicate the disease from the entire region.12

This campaign relied on mass vaccination strategies to interrupt the transmission of the virus. By scaling up immunization coverage and coordinating efforts across borders, the region saw a dramatic decline in cases. These successes served as a model for the global effort to eradicate the disease. Through these sustained public health interventions, the Western Hemisphere was officially declared free of indigenous polio in 1994.13