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Benefits of immunization

Summary

Safe water and proper sewage disposal, and vaccination are the two public health interventions that have had the greatest impact on the world's health. Thanks to pioneers such as Edward Jenner and Louis Pasteur, a handful of vaccines prevent illness or death for millions of people every year. Currently, it is estimated that immunization saves the lives of 3 million children per year but 2 million more lives could be saved by existing vaccines, if resources were available to provide universal coverage. The international community must devote the necessary resources, in terms of money and time, to maximize the promise that vaccinology holds for the relief of burden of disease.

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The science of vaccinology took off with the story of Edward Jenner, a country doctor living in Berkeley (Gloucestershire), England, who on 14 May 1796 performed the world’s first vaccination. Taking pus from a cowpox lesion on a milkmaid’s hand, Jenner inoculated an eight-year-old boy, James Phipps. Six weeks later Jenner variolated two sites on Phipps’s arm with smallpox, and the boy was not affected by this as well as subsequent exposures.
The history of vaccination as a deliberate endeavour began in the laboratory of Louis Pasteur. Louis Pasteur constructed the hypothesis that pathogens could be attenuated by exposure to environmental elements such as high temperature, oxygen and chemicals. His ensuing work on anthrax and rabies confirmed this hypothesis.
Meanwhile, the concept of antibodies and cellular immune responses had developed from the original work of Paul Ehrlich and Ilya Metchnikoff, respectively.
Paul Ehrlich developed the world's first synthetic pharmaceutical drug, Salvarsan (compound 606) for treating syphilis. Ehrlich's development of methods for specific quantification of antibodies made von Behring's passive immunity a practical reality. His concepts for specific complementarity of perceived cellular side chains with chemicals and with other proteins gave birth to what was later called specific receptor-ligand binding. This concept leads our understanding today of immunologic specificity, of cellular chemistry and of specific drugs.

The success of vaccines

Immunization of a large proportion of a population can lead to the protection of the entire population due to a ‘herd effect’ that slows down circulation of a pathogen in the immunized population. The greatest achievement of vaccination remains the eradication of smallpox, a disease that was responsible for 8 to 20% of all deaths in Europe before the introduction of vaccination. The number of diseases that can be prevented by vaccines is growing. Advances in biomedical research, technology, and government support for more publicly-funded immunization programs is helping to make this possible.
Vaccines still provide the most effective, longest-lasting method of preventing infectious diseases in all age groups. Today more than twenty-five diseases are now vaccine-preventable.
Table 1 shows the dates of introduction of the most commonly used vaccines, as monovalent preparations, as well as in combination with other vaccines.
Childhood immunization is one the most beneficial and cost-effective health interventions ever developed. Yet each year, millions of children living in the world’s poorest countries do not receive lifesaving vaccines. The World Health Organization estimates that more than 2 million people die each year from diseases for which immunization is routinely recommended, including measles, diphtheria, pertussis, and tetanus. Half of them are children under the age of 5

Table 1: Dates of introduction of commonly used vaccines
VaccineDate
Smallpox1796
Rabies1885
Cholera1896
Typhoid1896
Plague1896
Diphtheria (D)1923
Pertussis (Pw)1926
Tetanus (T)1927
Tuberculosis (BCG)1927
Yellow fever1935
Influenza1936
Polio (IPV)1955
DTPw1957
Polio (OPV)1958
DTIPV1961
Measles (M)1963
DTPIPV1966
Mumps (M)1967
Rubella (R)1969
MMR1971
Meningococcus1972
Pneumococcus1976
Acellular P (Pa)1981
Hepatitis B (HB)1981
Varicella (V)1984
rDNA HB1986
H. influenzae b (Hib)1988
Hepatitis A (HA)1991
DTPwIPVHib1993
DTPa1994
DTPwHB1996
HBHA1996
DTPaHib1997
DTPaIPVHib1997
Lyme1998
Rotavirus1998
Dtpa1999
HATy1999
DTPaHBIPV2000
DTPaHBIPVHib2000
MCCV2000
PCV2000
HPV/genital warts/Cervical cancer vaccine2006

Health improves wealth

Immunization is providing the opportunity to eliminate or significantly reduce common infectious diseases, to save lives and to reduce human suffering (Table 2). Economic evaluations indicate that many vaccination programs are cost-saving or cost-effective from the societal perspective.
There are several channels through which health improves wealth. The first is through its impact on education. Healthy children are better able to attend school and to learn effectively while in class. Studies have found that health interventions such as deworming programs and iron supplementation reduce absenteeism from school. The second channel is through the impact of health on productivity. Like schoolchildren, healthier workers have better attendance rates and are more energetic and mentally robust. Bloom et al. have calculated that a one-year increase in life expectancy improves labour productivity by 4 per cent. The third way by which health improves wealth is through its effect on savings and investment. Healthier people expect to live longer, so they have a greater incentive to save for retirement.
The savings booms in the East Asian “tiger” economies in the last quarter of the 20th century were largely driven by rising life expectancy and greater savings for retirement. The transition from high to low rates of mortality in many developing countries has been rapid. Largely brought about by medical and dietary improvements.

Table 2: Some of the major successes of vaccination
Smallpox, which had killed two million people per year until the late 1960s, was eliminated by 1979 after a massive worldwide immunization campaign.
The number of polio cases fell from over 300,000 per year in the 1980s to a mere 2,000 in 2002.
Two-thirds of developing countries have eradicated neonatal tetanus.
Since the launch of the World Health Organization’s Expanded Program on Immunization (EPI) in 1974, the number of reported measles deaths has dropped from 6 million to less than 1 million per year.
Pertussis (whooping cough) cases have fallen from 3 million per year to less than a quarter of a million.
Diphtheria cases have declined from 80,000 in 1975 to less than 10,000 today.
The Haemophilus influenzae type b (Hib) vaccine has reduced the incidence of Hib meningitis in Europe by 90 per cent in ten years.

Source: Advances in Vaccinology - October 15th, 2012 (last updated)