“…An encouraging observation while putting together this Special Issue has been the use of a variety of data sources to assess immunization inequalities. Studies have made use of traditional sources of immunization data like administrative data [ 19 , 23 , 32 ] and population surveys [ 18 , 21 , 22 , 27 , 29 , 30 ] (including Demographic and Health Surveys and/or Multiple Indicator Cluster Surveys [ 15 , 20 , 31 ]), while several other studies explored the potential of novel sources such as geospatial data [ 24 , 25 ], electronic immunization registries [ 34 ], dialogues [ 16 ], country appraisals and reports [ 35 ], and funding proposals [ 26 ]. Three review studies relied on synthesis and structured analyses drawing from a multitude of existing studies [ 17 , 33 , 36 ].…”