Chapter 116. Immunization Principles and Vaccine Use (Part 4)

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Principles of Vaccine Use Route of Administration Microbes differ in their routes of infection, patterns of transmission, and predispositions for certain age groups. The route of vaccine administration (oral, intranasal, intradermal, transdermal, subcutaneous, or intramuscular) takes these factors into account in order to maximize protection and minimize adverse events. Vaccine development is more a pragmatic undertaking than an exact science, guided only in part by immunologic principles and shaped largely by the results of clinical trials. While vaccines can theoretically be given by any route, each vaccine has unique characteristics adapted to a particular route and, in practice, must be given...

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Chapter 116. Immunization Principles and Vaccine Use (Part 4) Principles of Vaccine Use Route of Administration Microbes differ in their routes of infection, patterns of transmission, and predispositions for certain age groups. The route of vaccine administration (oral, intranasal, intradermal, transdermal, subcutaneous, or intramuscular) takes these factors into account in order to maximize protection and minimize adverse events. Vaccine development is more a pragmatic undertaking than an exact science, guided only in part by immunologic principles and shaped largely by the results of clinical trials. While vaccines can theoretically be given by any route, each vaccine has unique characteristics adapted to a particular route and, in practice, must be given by the licensed route, for which optimal immunogenicity and safety
have been documented. For example, vaccines containing adjuvants are designed for injection into the muscle mass. Mucosal administration of vaccines designed for parenteral administration may not induce good systemic responses because such vaccines do not induce mucosal secretory IgA. Administration of hepatitis B vaccine into the gluteal rather than the deltoid muscle may fail to induce an adequate immune response, while SC rather than IM administration of DTaP vaccine increases the risk of adverse reactions. Injectable biologicals should be administered at sites where the likelihood of local, neural, vascular, or tissue injury is minimized. Age Because age influences the response to vaccines, schedules for immunization are based on age-dependent responses determined empirically in clinical trials. The presence of high levels of maternal antibody and/or the immaturity of the immune system in the early months of life impairs the initial immune response to some vaccines (e.g., measles and pneumococcal polysaccharide vaccines) but not to others (e.g., hepatitis B vaccine). In the elderly, vaccine responses may be diminished because of the natural waning of the immune system, and larger amounts of an antigen may be required to produce the desired response (e.g., in vaccination against influenza). In contrast, in some age groups, the use of substandard amounts of antigen is sufficient for immunity induction and reduces the risk of adverse effects (e.g., a reduced dose of diphtheria
toxoid for persons ≥7 years of age). Age-related adverse events are discussed in a later section. Target Populations and Timing of Administration Disease attack rates differ across the human life span, and the timing of immunization must consider these variations along with the age-specific response to vaccines, the durability of the immune response, and the logistics for optimal identification and vaccination of the groups at risk. Aside from immunologic parameters, many factors are involved, including demographic features; thus, vaccination programs are really as much community as individual endeavors. Schedules for immunization are ultimately derived from careful consideration of the many relevant variables and may ultimately depend on the best opportunities to reach the target groups (e.g., infancy, school entry, puberty, college enrollment, military induction, entry into the workplace). Health care workers administering vaccines or caring for patients with vaccine-preventable diseases have a special responsibility to be adequately immunized themselves and to take all necessary precautions to minimize the risk of spreading infection (e.g., hand washing between immunizations or other interactions with patients). Catch-up immunization schedules for infants and children through the age of 18 years have been approved by the CDC (Fig. 116-3).
Figure 116-3 Catch-up immunization schedule for persons aged 4 months–18 years who start late or who are more than 1 month behind. 1. Hepatitis B vaccine (HepB). (Minimum age: birth) Administer the 3-dose series to those who were not previously vaccinated. A 2-dose series of Recombivax HB is licensed for children aged 11–15 years. 2. Rotavirus vaccine (Rota). (Minimum age: 6 weeks) Do not start the series later than age 12 weeks. Administer the final dose in the series by age 32 weeks. Do not administer a dose later than age 32 weeks. Data on safety
and efficacy outside of these age ranges are insufficient. 3. Diphtheria and tetanus toxoids and acellular pertussis vaccine (DTaP). (Minimum age: 6 weeks) The fifth dose is not necessary if the fourth dose was administered at age ≥4 years. DTaP is not indicated for persons aged ≥7 years. 4. Haemophilus influenzae type b conjugate vaccine (Hib). (Minimum age: 6 weeks) Vaccine is not generally recommended for children aged ≥5 years. If current age
recommended routinely at age 4–6 years but may be administered earlier if desired. Do not repeat the second dose in persons aged