Childhood Infectious Diseases, Immunization Impacts
Childhood Infectious Diseases, Immunization Impacts
Less than 100 years ago in the United States, a quarter of children died before their fifth birthday. Most of those died before reaching one year old. Today, the diseases that caused these deaths are rare in developed countries, and many American doctors have never treated a child with measles, polio, or diphtheria. The practice of immunizing children can claim a great deal of the credit for the miraculous reduction in childhood suffering and death during the last century.
The primary cause of infant and child deaths throughout recorded history has been infectious disease. For centuries, attempts to control infections included bloodletting, purging, use of leeches, or swallowing various concoctions of herbs and poisons. The epidemics of smallpox, measles, diphtheria, and pneumonia ignored these remedies and continued killing children.
In 1798, Edward Jenner (1749–1823) proved the effectiveness of vaccination as a strategy in preventing smallpox, and in 1956, the World Health Organization (WHO) in conjunction with national governments began a immunization program to eradicate smallpox from the world. The campaign was successful. In 1977, health officials in Somalia reported the last natural case of smallpox, and the WHO declared victory over smallpox in 1979.
The success of the smallpox campaign proved that effective immunization strategies could eradicate disease. Elimination of polio from North America in 1991 provided further proof that immunization is a powerful weapon for combating infectious diseases. While construction and production of vaccines can be quite complex, the idea behind how vaccines provide protection from disease is quite simple.
For centuries, medical practitioners knew that contracting a mild form of certain diseases protected against more severe forms of the same or similar diseases. The discovery that microorganisms caused infectious diseases provided a scientific foundation for this immunity phenomenon. When exposed to these microorganisms, the immune system will create specific neutralizing agents called antibodies. If the immune system produces antibodies fast enough, the body survives. Some microorganisms spread too rapidly however, and the body is overwhelmed before the immune system can react. At times the immune system does eventually stop the spread of the microorganism, but the body is so weakened that it never fully recovers. In some children, a second disease develops soon after the first, and the weakened body succumbs. Immunization primes the immune system to react quickly.
Active immunization is the process of inducing immunity without causing disease. A vaccine is a substance that when administered, induces the immune system to produce protective antibodies. Vaccines may be purified toxins, specific bacterial or viral proteins, genetically engineered pieces of the organism, or even whole-killed bacteria. The vaccine mimics the diseasecausing microorganism but does not cause disease. The vaccine fools the immune system to produce antibodies with little or no discomfort to the person. The immunity acquired may be life-long or may need repeated vaccine boosters to maintain protection.
Using the techniques developed early in the nineteenth century, vaccines for diphtheria, pertussis, tuberculosis, and tetanus entered the medical arsenal in the 1920s. When Jonas Salk (1914–1995) perfected injectable polio vaccine in 1955, parents waited in long lines to have their children vaccinated against polio. In the 1960s, an oral polio vaccine became available followed quickly by vaccines against measles, mumps, and rubella.
Despite the relative crude nature of the early vaccines, they provided effective control of many diseases and further refinement in vaccine design reduced side effects and reactions to the vaccines. Nations around the globe began widespread immunization programs in the latter part of the twentieth century. In 1962, the United States established a vaccination program coordinated by the federal government, and this program remains in existence, providing support to finance and administer a complete series of childhood vaccines. The Expanded Program on Immunization begun in 1974 by the WHO provides similar support worldwide for childhood vaccination.
While only smallpox has been eradicated, the impact of many diseases is a shadow of prior centuries. Immunization programs have virtually eliminated tetanus, diphtheria, measles, mumps, rubella, and Haemophilus influenzae type b meningitis from the United States. Experts at WHO estimate that the use of vaccines prevented more than two million childhood deaths in 2003.
These successes derive from the practices of giving vaccines to many children early in life. In many countries, school immunization laws facilitate active immunization of children against a core group of diseases prior to school entry. While the specific vaccinations vary from country to country, this core group recommended by WHO includes measles, polio, tetanus, pertussis, hepatitis B, and tuberculosis. Additionally, children receive vaccination against Haemophilus influenzae type b meningitis, rubella, and yellow fever in many countries.
Success in defeating infectious diseases depends on obtaining and sustaining high rates of immunization in children. No vaccine is 100% effective. Even if every child received vaccinations against all diseases, some children would remain susceptible. A phenomenon called “herd immunity” helps to protect those children who remain susceptible after vaccination. Herd immunity helps to halt the spread of disease by surrounding those susceptible children with many children who are immune. Immune children shield the susceptible children. Diseases do not spread effectively if most children are protected and only a few are not.
Immunization of children is extremely cost effective. Children are easy to find and gather in groups. Actual contact time with the medical provider is minimal. Immunization requires no change in lifestyle. The current widely used vaccines produce few side effects or reactions. In the United States, every dollar invested saves between $2 and $27 in medical costs to treat infectious diseases.
Immunization programs do save lives, yet major efforts remain. An estimated 1.4 million children died worldwide in 2002 from vaccine-preventable diseases. Measles accounted for a third of the deaths and Haemophilus influenzae another third, while pertussis and neonatal tetanus killed most of the remainder. Many more children die from diseases potentially preventable by vaccines. For example, rotavirus causes the most common type of diarrheal disease worldwide. A new vaccine has recently become available to prevent rotavirus diarrhea that, if used worldwide, would prevent about 500,000 childhood deaths in developing nations annually. Use of a vaccine to prevent childhood pneumonia would save the lives of about two million children annually. Researchers work diligently to produce vaccines for the diseases such as malaria and HIV that are ravaging both adults and children. New forms of old diseases continue to emerge, and continued surveillance and research is a high priority.
Some problems have developed while trying to continue the remarkable success of immunization programs obtained in the twentieth century. Many citizens of developed countries consider themselves safe because so few get sick from epidemic diseases such as polio or diphtheria, and vaccination rates have been dropping in developed countries as a result. Until a disease disappears from the world, no country can consider itself safe. No disease is more than an airplane trip away from anyone. If the percentage of immune individuals declines, the risk of epidemic disease skyrockets.
Compared to a century ago, the practice of immunization has reduced the burden of infectious disease worldwide. Children have benefited the most, with millions more children surviving to adulthood. The challenges for the twenty-first century include maintaining the progress, expanding the scope, and moving toward eventual eradication of infectious diseases. Complacency only benefits the disease-causing organisms in this war.
In the following article in Atlantic Monthly magazine, Arthur Allen relates the story of a community in Colorado that has experienced outbreaks of pertussis (whooping cough) and other preventable diseases after parents chose not to vaccinate their children according to state recommendations.
As most of a population becomes vaccinated, a herd-immunity effect provides some protection to those who are unvaccinated. As Allen relates, this herd immunity is not enough to prevent outbreaks of infectious disease. Arthur Allen, a Washington-based journalist, is also the author of Vaccine: The Controversial Story of Medicine's Greatest Lifesaver.
Cohen, Stuart A. “On the Precipice: Private-Sector
Vaccine Delivery.” Pediatric News 40 (April 1, 2006).
Lloyd Scott Clements