Immunization against diseases of public health importance

The benefits of immunization

Vaccines — which protect against disease by inducing immunity — are widely and routinely administered around the world based on the common-sense principle that it is better to keep people from falling ill than to treat them once they are ill. Suffering, disability, and death are avoided. Immunization averted about two million deaths in 2002. In addition, contagion is reduced, strain on health-care systems is eased, and money is frequently saved that can be used for other health services.

Immunization is a proven tool for controlling and even eradicating disease. An immunization campaign carried out by the World Health Organization (WHO) from 1967 to 1977 eradicated the natural occurrence of smallpox... Since the launch by WHO and its partners of the Global Polio Eradication Initiative in 1988, polio infections have fallen by 99%, and some five million people have escaped paralysis. Between 2000 and 2008, measles deaths dropped worldwide by 78%.

Commonly used vaccines

Routine vaccination is now provided in all developing countries against measles, polio, diphtheria, tetanus, pertussis, and tuberculosis. To this basic package of vaccines, which served as the standard for years, have come new additions, such as hepatitis B vaccine.  In industrialized countries a wider span of protection is typically provided, often including vaccines against influenza, predominant strains of pneumococcal disease, and mumps (usually in combination with measles and rubella vaccine). Immunization programmes may be aimed at adolescents or adults — depending on the disease concerned — and at infants and children.

Global immunization coverage

Globally, coverage has greatly increased since WHO's Expanded Programme on Immunization began in 1974. In 2003, global DTP3 (three doses of the diphtheria-tetanus-pertussis combination vaccine) coverage was 78% — up from 20% in 1980.  However, an estimated 2.1 million people around the world, including 1.4 million children under age five, still died in 2002 of diseases preventable by widely used vaccines.

Effectiveness and safety

All vaccines used for routine immunization are very effective in preventing disease, although no vaccine attains 100% effectiveness. More than one dose of a vaccine is generally given to increase the chance of developing immunity.  Vaccines are very safe, and side effects are minor ─ especially when compared to the diseases they are designed to prevent. Serious complications occur rarely.  For example, an immediate severe allergic reaction to measles vaccine (anaphylaxis) occurs in less than one case per million doses given.

The cost-effectiveness of immunization

Immunization is considered to be among the most cost-effective of health investments. A recent study estimated that a one-week "supplemental immunization activity" against measles carried out in Kenya in 2002 ─ in which 12.8 million children were vaccinated — would result in a net saving in health costs of US$ 12 million over the following ten years; during that time it would prevent 3 850 000 cases of measles and 125 000 deaths.