Why Reaching Zero-Dose Children Holds the Key to Achieving the Sustainable Development Goals.

Immunization has one of the highest coverage levels of any health intervention, yet there remain zero-dose children, defined as those who do not receive any routine immunizations. There were 18.2 million zero-dose children in 2021, and as they accounted for over 70% of all underimmunized children, reaching zero-dose children will be essential to meeting ambitious immunization coverage targets by 2030. While certain geographic locations, such as urban slum, remote rural, and conflict-affected settings, may place a child at higher risk of being zero-dose, zero-dose children are found in many places, and understanding the social, political, and economic barriers they face will be key to designing sustainable programs to reach them. This includes gender-related barriers to immunization and, in some countries, barriers related to ethnicity and religion, as well as the unique challenges associated with reaching nomadic, displaced, or migrant populations. Zero-dose children and their families face multiple deprivations related to wealth, education, water and sanitation, nutrition, and access to other health services, and they account for one-third of all child deaths in low- and middle-income countries. Reaching zero-dose children and missed communities is therefore critical to achieving the Sustainable Development Goals commitment to "leave no one behind".