Global routine vaccination coverage 2011
In 1974, WHO established the Expanded Programme on Immunization to ensure that all children had access to routinely recommended vaccines.1 Global coverage with the third dose of diphtheria–tetanus–pertussis vaccine (DTP3) was <5% in 1974 and increased to 79% by 2005; however, more than one-fifth of the world’s children, especially those in low-income countries, were still not fully vaccinated. In 2005, WHO and UNICEF developed the Global Immunization Vision and Strategy (GIVS) to improve national immunization programmes and decrease morbidity and mortality associated with vaccinepreventable diseases.2 One goal of the strategy was that all countries achieve and sustain 90% national DTP3 coverage.
This report summarizes global routine vaccination coverage during 2011. An estimated 83% of infants worldwide received at least 3 doses of DTP vaccine in 2011, similar to coverage in 2009 (83%) and 2010 (84%). Among 194 WHO member states, 130 (67%) achieved ≥90% national DTP3 coverage. However, 22.4 million children were incompletely vaccinated at 12 months of age and remained at risk for vaccine-preventable morbidity and mortality. More than half of all incompletely vaccinated children live in 3 countries: India (32%), Nigeria (14%), and Indonesia (7%). Among all incompletely vaccinated children, 62% never received the first DTP dose (DTP1), and 38% started but never completed the series. Strengthening routine immunization services, especially in countries with the greatest number of under-vaccinated children, should be a global priority to help achieve the fourth Millennium Development Goal, to reduce mortality among children <5 years of age by two-thirds from 1990 to 2015.
Vaccination coverage is calculated as percentage of those in the target age group who received a dose of a recommended vaccine by a given age. DTP3 coverage by age 12 months is a major indicator of immunization programme performance, but coverage with other vaccines, such as third dose of oral polio vaccine (OPV3) or first dose of measles-containing vaccine (MCV1) is also considered. Administrative coverage estimates are derived by dividing the number of vaccine doses administered to children in the target age group by the estimated target population. These are reported annually to WHO and UNICEF by 194 WHO member states through the Joint Reporting Form. Further estimates of vaccination coverage can be obtained from coverage surveys in which a representative sample of households is visited to identify children in the target age group, and dates of receipt of vaccine doses are copied from the child’s vaccination card. If the card is not available, a caregiver is asked to recall whether the child received a particular vaccine dose. WHO and UNICEF derive national estimates of vaccination coverage through an annual country-by-country review of all available data, which may include revision of the historical coverage time series. These estimates are updated and published annually on the WHO website.
During 2011, while 130 (67%) countries achieved ≥90% national DTP3 coverage, only 46 (24%) achieved the GIVS goal of ≥80% DTP3 coverage in every district. DTP3 coverage was 80%–89% in 32 (17%) countries, 70%–79% in 13 (7%) countries, and <70% in 19 (10%) countries (Table 1).
By the end of 2011, hepatitis B vaccine was introduced into routine childhood vaccination schedules in 180 (93%) countries; 94 (52%) recommended the first dose within 24 hours of birth to prevent perinatal transmission of hepatitis B virus infection. Coverage with 3 doses of Haemophilus influenzae type b vaccine (Hib3), which had been introduced in 177 (91%) countries by 2011, was 43% globally, ranging from 11% (South-East Asia Region) to 90% (Region of the Americas). By 2011, rotavirus vaccine had been introduced in 31 (16%) countries, and pneumococcal conjugate vaccine (PCV) in 72 (37%) countries.
Administrative coverage estimates are convenient and timely, but may overestimate or underestimate coverage if there are inaccuracies in the numerator (i.e. doses administered) or denominator (i.e. census data). While coverage surveys are not dependent on knowledge of target population size or on other administrative data sources, they are costly and, because they are retrospective, are not timely. Further, accuracy and precision of coverage survey estimates decrease as proportion of cardholders decreases. Unfortunately, the prevalence of cardholders is low in many countries. 6 In 87 countries with available card prevalence data from demographic and health surveys or multiple indicator cluster surveys since 2000, the median prevalence of cardholders was 72% (range: 8%–99%), but prevalence was <70% in 21 of the 33 least-developed countries (according to World Bank classification) (median: 62%; range: 8%–93%).
Coverage surveys are useful for validating administrative data and for monitoring coverage at different administrative levels, to aid in identifying areas of low coverage. WHO recommends that countries conduct regular vaccination coverage surveys to validate reported administrative coverage. A WHO advisory committee recommends validation of vaccine coverage estimates, ideally using multiple external data sources such as serosurveys, mortality and morbidity data.
Among all incompletely vaccinated children worldwide, 14 million (62%) had not received the first DTP dose. Nearly 8.4 million received at least one DTP dose, but dropped out before completing the 3-dose series. The factors associated with under-vaccination may be different from those associated with non-vaccination.8 For example, immunization system issues are more commonly reported with under-vaccination while access to services, parental attitudes, knowledge and practices appear to play a greater role among children who have not received any vaccination. For improvements in global vaccination coverage to occur, multifaceted and tailored strategies will be required by countries to address the factors contributing to incomplete infant vaccination, particularly among countries with the largest number of unvaccinated children.
More than half of incompletely vaccinated children live in 3 countries (India, Nigeria and Indonesia). Focusing routine immunization efforts in countries with the highest number of unvaccinated children should substantially reduce the number of susceptible children worldwide and limit the occurrence and spread of vaccine-preventable disease outbreaks. As part of the Decade of Vaccines launched in 2010, a global vaccine action plan was adopted by all WHO member states at the World Health Assembly in May 2012.9 Meeting routine vaccination coverage targets in every region, country and community worldwide is a major goal of this plan.