The 2024 Special Issue of Inequality in Immunization collates 14 global research and review contributions that spotlight differences in the attainment of immunization coverage across population groups, capturing findings pertaining to various types of immunization (including COVID-19 and childhood immunization). The articles pose key questions about methodological and definitional issues, such as how to standardize and adapt framing to measure zero dose and how to measure the significance of parental hesitancy in exacerbating inequalities. The contributions within this Special Issue range from research studies that are global in scope to analyses focused on national and subnational settings. This collection represents some of the latest state-of-the-art scientific works on inequalities in immunization available in 2024, with contributions from a range of academics, scientists, and implementers involved in networks of and collaboration between the World Health Organization, Gavi, the Vaccine Alliance, as well as the US Centers for Disease Control.