West/Central Africa needs to take the most urgent action to improve immunization coverage. It has by far the lowest coverage in the world - just 52 per cent of children in 2003 were reached with measles vaccine through routine immunization services - but it also failed to register any improvement at all between 1990 and 2003.
The region also has by some distance the highest under-five mortality rate, with 193 child deaths per 1,000 live births, compared with an average of 87 per 1,000 live births for all countries in the developing world.
Only three of the region's countries are likely to achieve the goal of 90 per cent immunization against measles - Gambia, which has already attained the target, plus Ghana and Sao Tome and Principe, which are considered on course to achieve it by 2010. All the other 21 countries require major improvements.
Routine measles immunization coverage is just 35 per cent in the Central African Republic and Nigeria, making them the two countries in the world with the lowest coverage against measles; the average annual rate of increase needed in both countries will be 7.9 percentage points. In both these countries, moreover, along with Burkina Faso, Cape Verde, Congo, Equatorial Guinea, Gabon and Togo, immunization coverage actually declined between 1990 and 2003.
The situation is particularly disturbing in Nigeria because of that country's large population: with 2.9 million children under one year of age unprotected against measles, it has more unimmunized children than any other country in the world except India.
Emergencies, instability and insecurity in half of the region's countries are major constraints to developing regular immunization activities. Another constraint is lack of funds to finance vaccines for routine immunization. Of the 24 countries in the region, eight depend entirely on external donors to finance the traditional EPI vaccines and to support immunization activities.
A lack of health personnel to implement immunization activities at district and peripheral levels is another major cause of low performance, especially in countries covering large geographic areas and in which there are difficulties in reaching remote areas.
Nevertheless, there have been many positive achievements. Notable improvements over the period 1990 to 2003 include Niger, with 3 percentage points gained in measles immunization coverage each year, and Mauritania, with 2.5.
The Measles Initiative supported nationwide campaigns in 2004 in an effort to supplement low routine immunization coverage and speed mortality reduction. Burkina Faso, Mali, Mauritania and Togo all achieved near universal coverage.