Why will Jane and John Jones born in 2010 and 2011 respectively live four score years or longer?
Vaccination as a deliberate attempt to protect humans against disease has a short history.
In spite of this, vaccination has had a major effect on the reduction of mortality and length of life
Since the time of Edward Jenner (Figure 1), vaccination has eliminated smallpox. Smallpox was greatly feared as the leading cause of death in the western world in the 18th century. Because of the high mortality with smallpox (25%), the practice of variolation with the smallpox virus had been practiced in eastern societies and was introduced in Britain in 1721. However the subsequent infection was occasionally severe with a mortality of 1 to 2%.
In 1798, Jenner introduced vaccination with cowpox vaccine as protection against smallpox which rapidly replaced variolation. Although many were anxious regarding vaccination (Figure 2) and in spite of an anti-vaccination campaign, vaccination was rapidly accepted. During the 19th and first half of the 20thcenturies the methods of vaccination continued to be refined (Figure 3) and the quality of the vaccine improved. A worldwide vaccination campaign eliminated this disease as of 1979.
Poliomyelitis was first recognized in 1840 and the polio virus was identified in 1908. Polio was an endemic pathogen until 1880s when major epidemics began to occur in Europe; soon after widespread epidemics appeared in America. Major polio epidemics were one of the most dreaded childhood diseases in the 20thcentury.
Poliomylelitis is highly contagious but fortunately many infections do not affect the central nervous system. The poliomyelitis infection that does spreads along certain nerve pathways and destroys motor neurons leading to spinal polio in 79% and bulbospinal polio in 21%. The latter required management in the iron lung, a symbol of seriousness of this infection. (Figure 4) Vaccines to prevent polio included the Salk vaccine, an inactivated polio vaccine in 1952, and the Sabin vaccine, a live attenuated oral vaccine in 1955 that became the vaccine of choice in 1962. Worldwide use of this vaccine has largely eliminated this distressing disease.
Vaccines introduced in the 20th century have limited 9 other major diseases in parts of the world: diphtheria, tetanus, yellow fever, pertussis, measles, mumps, rubella, typhoid and rabies.
Influenza, a viral infectious disease, spreads around the world in seasonal epidemics resulting in the deaths of between 250,000 to 500,000 people each year. Three major pandemics in the 20th century have led to millions of deaths, each due to a new strain of the virus.
Vaccination against influenza is made available each year in Canada. The trivalent influenza vaccine contains purified and inactivated antigens and has a vey low reactivity. The challenge each year is that the influenza virus evolves rapidly and new strains replace the virus of the previous year. Thus new vaccines are constantly created.
It is important to support vaccination programs.
Remember: “An ounce of prevention is worth a pound of cure”