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Upon completion of the chapter, the reader will be able to:
Define vaccination and immunization.
Discuss the impact individual vaccines have on public health.
Recommend an immunization schedule for a child, including immunocompromised children.
Recommend an immunization schedule for an adult based on comorbid conditions and lifestyle choices.
Evaluate an adverse reaction and its probable association with a vaccine.
The development and widespread use of vaccines is one of the greatest public health achievements of the 20th century. Other than safe drinking water, no other modality has had a greater impact on reducing mortality from infectious diseases.1 The first accounts of deliberate inoculation to prevent disease date back as far as the 10th century. However, it wasn’t until 1798 that Edward Jenner published his work on inoculation of natural cowpox as a means to prevent smallpox infection that documented the first scientific attempt at prevention by inoculation. Since 1900, the widespread use of vaccines has resulted in the eradication of smallpox worldwide and wild-type poliovirus from the Western hemisphere. There have also been dramatic declines in the incidence of diphtheria, pertussis, tetanus, measles, mumps, rubella, and Haemophilus influenzae type b infections.2 In the United States, there are immunization recommendations against 17-vaccine preventable diseases affecting all age groups.
Vaccines have traditionally been preparations of killed or attenuated microorganisms that provide active immunity against a variety of viral and bacterial infections. Most vaccines are designed to prevent acute infections that can be rapidly controlled and cleared by the immune system. Successful immunization involves activation of antigen-presenting cells with processing of the antigen by lysosomal or cytoplasmic pathways. T and B lymphocytes will be activated to replicate and differentiate to form large pools of memory cells for protection against subsequent exposure to the antigen.2
Vaccines against viral infections may be attenuated live viruses or inactivated viral particles. Attenuation may be accomplished by several methods to decrease the viruses’ virulence while retaining their immunogenicity. Bacterial vaccines utilize antigenic particles of the outer membrane to elicit an immune response. Outer membrane polysaccharides are poorly immunogenic in children younger than 2 years unless conjugated with a carrier protein. Also, bacterial toxins may undergo chemical treatment to render them nontoxic to form toxoids against infectious agents.
Often the terms vaccination and immunization are used interchangeably even though they are distinct concepts. Vaccination refers to the act of administering a vaccine, whereas immunization refers to the development of immunity to a pathogen. The delivery of a vaccine does not imply that the individual mounted an adequate immune response to the vaccine to elicit protection. However, immunization implies that the act of vaccination resulted in the development of protective immunity.