Since the launch of the global Expanded Programme on Immunization (EPI) in 1974, vaccination against 6 diseases (tuberculosis, polio, diphtheria, tetanus, pertussis, and measles) has prevented millions of deaths and disabilities. Significant advances have been made in the development and introduction of vaccines; licensed vaccines are now used for the prevention of 25 diseases. Historically, new vaccines became available in low- and middle-income countries only decades after their introduction in high-income countries. Today, however, vaccines are being introduced more rapidly thanks to support from global partners, including WHO and UNICEF, who assist in prequalifying and procuring vaccines, and the GAVI Alliance (GAVI), which provides funding and influences vaccine markets through forecasting and assurances of demand in low-income countries in exchange for lower vaccine prices. This report uses data from 194 countries on vaccine introduction obtained from the WHO immunization data website; the status of new