Overview of global, regional, and national routine vaccination coverage trends and growth patterns from 1980 to 2009: implications for vaccine-preventable disease eradication and elimination initiatives.

The Expanded Program on Immunization (EPI) began in 1974 with the goal of ensuring that all children benefit from life-saving vaccines [1]. Vaccination coverage is a key indicator of vaccination program performance, and coverage for the third dose of diphtheria-tetanus-pertussis–containing vaccine (DTP3) is often used as the main indicator for performance of routine vaccination services. Strong routine vaccination services, as measured by high DTP3 vaccination coverage, are critical for successful implementation of key global public health goals. For instance, strong routine vaccination is one of the 4 core strategies for reaching and sustaining polio eradication in the 2010–2012 strategic plan of the Global Polio Eradication Initiative (GPEI) [2, 3]. By 2009, global DTP3 coverage reached 83%, indicating the commitment by many countries to reduce mortality and morbidity from vaccine-preventable diseases (VPD). In 2000, the World Health Organization (WHO) and the United Nations Children's Fund (UNICEF) began a process of annually estimating global, regional, and national routine vaccination coverage across multiple vaccines, including DTP vaccine, polio vaccine (POL), and measles-containing vaccine (MCV). These estimates, which are updated annually, are based on officially reported data from government administrative sources, coverage surveys, and other published and unpublished work [4]. WHO and UNICEF also undertook a retrospective review of these sources to estimate vaccination coverage for 1980–1999. These estimates are used for a wide variety of reasons, including global pay-for-performance incentives, tracking the attainment of key child survival goals, and immunization program objectives and estimates of general changes in infant and child mortality [5–8]. Although these estimates are generally considered the most reliable source of coverage, concerns have been raised about the accuracy of the administrative sources used in the estimates, compared with coverage survey sources [9]. These vaccination coverage estimates provide an opportunity to assess the historical performance of national and regional vaccination services. Generally, analyses of program performance are limited to a brief synopsis of changes in coverage since the previous year [10]. However, benefits exist in an in-depth analysis of the historical performance of vaccination programs worldwide, including how vaccination coverage has varied over time, how varying levels of coverage affect annual changes in coverage, and how coverage has varied between different geographical regions. Such analysis would be informative for the further development of polio, measles, and other vaccine-preventable disease elimination and eradication goals, routine vaccination performance goals, and the application of routine vaccination strategies based on the existing level of performance of a country's vaccination program. Specifically, the 2013–2018 Polio Eradication and Endgame Strategic Plan includes the strengthening of immunization systems as one of 4 objectives to boost immunity and help wide-scale introduction of inactivated polio vaccine (IPV) [10]. The main indicator of this objective is achievement of a ≥10% annual increase in DTP3 coverage in 80% of high-risk districts of key polio-focus countries between 2014 and 2018 [11]. We studied 1980–2009 vaccination coverage data and assessed (1) the annual mean rate of change in vaccination coverage for countries in each geographic region, (2) the number of years needed to reach various coverage levels by each region, and (3) variability in the annual rate of change in vaccination coverage levels, based on the existing level of vaccination coverage.