Introduction

In both industrialized and developing countries, child immunization has become one of the most important and cost-effective public health interventions [1, 2]. National immunization programs have prevented millions of deaths since WHO initiated the 'Expanded Program on Immunization (EPI)' in 1974 [3]. Smallpox was eradicated in 1979 [4], poliomyelitis is on the verge of eradication [5], and two thirds of developing countries have eliminated neonatal tetanus (NT).1 Global immunization coverage, as measured by the reported infant coverage with the third dose of diphtheria-tetanus-pertussis (DTP) vaccine (DTP3), was at 78% worldwide in 2005 [6] (Fig. 1), as compared to 20% in 1980. By the end of 2004, 153 of 192 WHO Member States had introduced hepatitis B (HepB) vaccine and 92 countries had introduced Haemophilus influenzae type b vaccine (Hib) into routine infant vaccination programs [7, 8], even though both vaccines are still underused in developing countries. The estimated number of deaths (from measles, pertussis and NT) prevented through childhood immunization in 2003 was more than 2 million. Infant HepB vaccination in 2003 was estimated to prevent a future 600 000 adult deaths, which would have occurred without vaccination, due to chronic liver disease and liver cancer.

However, the failure to reach > 20% of the world's children with existing vaccines was responsible for at least 2.5 million of an estimated 10.5 million deaths of children < 5 years in 2002 (Fig. 2), mainly in developing countries. Of these deaths, 1.4 million could have been prevented by vaccines currently recommended by WHO: > 500 000 due to measles, nearly 400 000 due to Hib, nearly 300 000 due to pertussis, and 180 000 NT deaths [9, 10]. An additional 1.1 million children < 5 years are estimated to have died worldwide in 2003 from rotavirus and pneumococcal disease, against which effective vaccines exist,2 but are not yet used in developing countries [10]. Through their impact on childhood morbidity and mortality, immunization programs are already contributing considerably to reaching the 'Millennium Development Goal 4' - a two-third reduction of < 5 mortality by 2015 [11]. It was estimated that improving coverage with the basic six EPI vaccines could potentially reduce < 5 mortality by 13%, with another 10% mortality reduction possible following the introduction and more widespread use of Hib, pneumococcal, rotavirus and meningococcal vaccines.

In industrialized countries, mortality reduction is not the main driving force of national vaccine programs. Programs in wealthy countries recognize and mostly adhere to global vaccination goals set by WHO, and address

1 WHO Geneva: Maternal and neonatal tetanus (MNT) elimination web site at http://www. who.int/immunization_monitoring/diseases/MNTE_initiative/en/index2.html

2 See the chapter by Dr. Steele of this volume on rotavirus and section on pneumococcal vaccines later in this chapter

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Global

—9— Central Europe, CIS

--Industrialized countries

—A— East Asia and Pacific

■ ■ - ■ Latin America and Caribbean

O Mid-East and N Africa

— - — South Asia

Sub Saharan Africa

Figure 1. Annual third dose of diphtheria-tetanus-pertussis vaccine (DTP3) coverage globally and by Region, 1980-2005. Source: WHO/UNICEF estimates, 2006

Figure 2. Percentage of deaths from vaccine-preventable diseases (VPDs) globally among children < 5 years, by disease, 2002. An estimated 2.5 million deaths of children < 5 years worldwide (of a total of 10.5 million deaths in this age group) are caused by diseases for which vaccines are currently available. (t) Diphtheria, hepatitis B (HepB), Japanese encephalitis, meningococcal disease, poliomyelitis, and yellow fever. In older age groups, approximately 600 000 HepB deaths are preventable by routine immunization.

Figure 2. Percentage of deaths from vaccine-preventable diseases (VPDs) globally among children < 5 years, by disease, 2002. An estimated 2.5 million deaths of children < 5 years worldwide (of a total of 10.5 million deaths in this age group) are caused by diseases for which vaccines are currently available. (t) Diphtheria, hepatitis B (HepB), Japanese encephalitis, meningococcal disease, poliomyelitis, and yellow fever. In older age groups, approximately 600 000 HepB deaths are preventable by routine immunization.

potential life years saved through vaccination in cost-effectiveness analyses. Main motivators for vaccination programs in industrialized countries are morbidity reduction and improvements in quality of life, indirect societal savings and also moral causes [12]. As for vaccination programs anywhere in the world, the access to the best and most effective vaccines available is seen as a right of every child.

Rapid progress in understanding of infectious disease pathogenesis, immunology, and biotechnology has increased the number of candidate vaccine antigens available, many of which have entered clinical phases of testing for safety, immunogenicity and eventually efficacy. Pressures are growing on public health decision makers, advisers and implementers to establish transparent and evidence-based ways to decide which new vaccines can and should be introduced on a large scale into national immunization programs. While the gap in access to new vaccines between the developing and industrialized world remains wide (see below), rich countries are still the first to introduce and use new vaccines. This is illustrated by the recent licensing of the first human papilloma virus (HPV) vaccine (see later in this chapter), the second possibly cancer-preventive vaccine since HepB. HPV vaccine is now being recommended by the Advisory Committee of Immunization Practices to be included into the U.S. immunization program.

Interest in vaccination programs from countries and partner agencies continues to be strong, due to the cost effectiveness and measurable public health impact of vaccination, particularly on recent progress towards global polio eradication [5] and measles mortality reduction. Other reasons for which vaccination remains a high priority in public health are the rapid progress in biotechnology and vaccine development, and the emergence of global infectious disease threats, including HIV/AIDS, SARS, and influenza. The establishment of the Global Alliance for Vaccines and Immunization (GAVI) in 2000 [13] has focused global activities to support vaccination programs through raising considerable funds, and assisting especially poorer countries in improving and expanding their vaccination programs. WHO and UNICEF, together with other immunization partners, have recently elaborated a long-term strategic plan for 2006-2015, the Global Immunization Vision and Strategy (GIVS) [8], to guide country programs and coordinate efforts of the international immunization partnership.

This chapter describes the main currently used global immunization policies and strategies, discusses progress towards improving access of all children to vaccines worldwide, including remaining gaps between developing and industrialized countries, and provides short updates on the current status of priority and new vaccines.

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