Trends in differences between births and surviving infants reported for immunization program planning and external data sources in Eastern and Southern Africa 2000-2013.

To inform our WHO team's support for immunization programs in Member States in Eastern and Southern Africa, we compared annual trends from 2000 to 2013 in target populations reported by Member States through the WHO-UNICEF joint reporting form with United Nations (UN) population projections and modeled infant mortality estimates from the UN Inter-agency Group for Child Mortality Estimation. Our findings indicated a tendency of underestimating births and surviving infants used by Member States as denominators for administrative immunization coverage rates, resulting in or contributing to overestimation of coverage. The difference with UN estimates appeared to be more pronounced for surviving infants than births. Measures of central tendency for individual country differences indicated that those differences decreased over time. Comparing trends of births and surviving infants with external sources can help monitoring progress in efforts to provide accurate and reliable target population estimates and sampling frames.