viernes, 29 de octubre de 2010
Global Routine Vaccination Coverage, 2009
October 29, 2010 / 59(42);1367-1371
The widespread use of vaccines has greatly improved global public health, preventing millions of childhood hospitalizations and deaths each year. Vaccination of children also is projected to avert adult deaths through the prevention of hepatitis B (HepB) virus--related chronic liver disease and liver cancer (1) and human papilloma virus--related cervical cancer (2). When the World Health Organization (WHO) began the Expanded Programme on Immunization in 1974, <5% of the world's children had been fully vaccinated with bacille Calmette-Guérin (BCG), diphtheria-tetanus-pertussis (DTP) vaccine, oral poliovirus vaccine, and measles-containing vaccine (MCV) during the first year of life (3). Since then, increased vaccination coverage has resulted in substantial reductions in morbidity and mortality, including a >99% decline in polio incidence since 1988 (4), with eradication on the horizon, and a 78% decline in measles-associated mortality from 2000 to 2008 (5). With the introduction of Haemophilus influenzae type b (Hib) vaccine, HepB vaccine, pneumococcal conjugate vaccine (PCV), and rotavirus vaccine into many countries' routine vaccination schedules, further reductions in morbidity and mortality are expected. However, based on an annual global birth cohort of approximately 130 million, an estimated 23 million infants worldwide still do not receive the benefits of routine vaccination (i.e., 3 doses of DTP during the first year of life). The Global Immunization Vision and Strategy (GIVS), developed in 2005 by WHO and UNICEF, assists countries in strengthening immunization programs and vaccinating more persons. GIVS aims to achieve 90% national 3-dose DTP (DTP3) coverage by age 12 months in all countries, and 80% coverage in every district or equivalent administrative unit by 2010 (and to sustain these levels through 2015 ). This report summarizes global routine vaccination coverage during 2000--2009 and progress toward achieving GIVS goals.
Methods for Estimating Routine Vaccination Coverage
Routine vaccination coverage levels indicate recent immunization program performance and population immunity. Coverage usually is assessed based on the percentage of children who received a specified number of doses of a recommended vaccine during the first year of life. This is in contrast to mass vaccination campaigns or other supplemental vaccine activities that do not record vaccine doses administered. Vaccination coverage is estimated using a number of methods. Administrative vaccination coverage is calculated by dividing vaccine doses reported to have been administered to the target population by the total estimated target population. Aggregated administrative data are analyzed at the national level, and national coverage data are reported annually to WHO and UNICEF on the Joint Reporting Form on Immunization (JRF), a standard questionnaire that was developed in 1998 and is sent to all 193 WHO member states.* Vaccination coverage estimates are then reported on the WHO website.†
In many countries, household vaccination coverage surveys are conducted to validate administratively reported data. A representative sample of households is selected, and vaccination coverage is determined by examining the child's immunization card or by parental recall. WHO and UNICEF systematically review data from sources including government JRF reports, published and unpublished reports, coverage surveys, and consultation with local experts, to derive annual estimates of national coverage with recommended vaccines§ (7). DTP3 coverage by age 12 months is the agreed-upon indicator of immunization program performance. In addition to DTP3, coverage with the first MCV dose (MCV1) is an indicator used to monitor progress toward the fourth Millennium Development Goal of reducing mortality among children aged <5 years by two thirds (from 1990 levels) by 2015.¶
Estimated Routine Vaccination Coverage, 2009
Estimated global DTP3 coverage in the 193 WHO member states increased from 74% in 2000 to 82% in 2009, reflecting the vaccination of 107.1 million infants with 3 doses of DTP vaccine in 2009 (14.6 million more than in 2000). Changes in coverage varied by geographic region, and the overall increase mainly was attributed to improvements in vaccination coverage in the African (+16%), Eastern Mediterranean (+12%), and Western Pacific (+10%) WHO regions (Figure 1). National DTP3 coverage of ≥90% was reported by 122 (63%) countries, but only 48 (25%) reported ≥80% coverage in all districts, and only 55% of low-income countries are on track to achieve 90% coverage by 2015 (UNICEF, unpublished data, 2010). During 2007--2009, 149 (77%) countries had sustained DTP3 coverage of ≥80% (Figure 1); however, coverage in 2009 was <80% in 36 (19%) countries, and six countries failed to achieve 50% DTP3 coverage. Among the 23.2 million children worldwide who did not receive 3 doses of DTP vaccine during the first year of life in 2009, 70% live in 10 countries, with approximately half in India (37%) and Nigeria (14%) (Figure 2).
From 2000 to 2009, estimated global MCV1 coverage increased from 71% to 82%, and 136 (70%) countries added a second MCV dose to their routine vaccination schedules. Three-dose coverage with HepB vaccine (HepB3) increased from 30% to 70% during this period, and 3-dose coverage with Hib vaccine (Hib3) increased from 13% to 38%. In countries where Hib vaccine had been introduced, Hib3 coverage was similar to DTP3 coverage; however, a commensurate increase in global coverage did not occur because several large countries (e.g., China, India, Indonesia, and Nigeria) had not yet introduced Hib vaccine (Figure 3).
Dept of Immunization, Vaccines, and Biologicals, World Health Organization, Geneva, Switzerland. United Nations Children's Fund, New York, New York. Global Immunization Div, National Center for Immunization and Respiratory Diseases, CDC.
Global Routine Vaccination Coverage, 2009