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Chapter 116. Immunization Principles and Vaccine Use (Part 5)

For common and highly communicable childhood diseases such as measles, the target population is the universe of susceptible individuals, and the time to immunize is as early in life as is feasible and effective. | Chapter 116. Immunization Principles and Vaccine Use Part 5 For common and highly communicable childhood diseases such as measles the target population is the universe of susceptible individuals and the time to immunize is as early in life as is feasible and effective. In the industrialized world immunization with live-virus vaccine at 12-15 months of age has become the norm because the vaccine protects 95 of children immunized at this age and there is little measles morbidity or mortality among infants 1 year of age. In contrast under crowded conditions in the developing world measles remains a significant cause of death among young infants. For optimal benefit in this situation it is necessary to immunize early enough to narrow the window of vulnerability between the rapid decline of maternal antibody 4-6 months after birth and the development of vaccine-induced active immunity this choice must be made despite the less efficient immune response in children 1 year old. Invasive infections due to Hib meningitis pneumonia and epiglottitis occur primarily in young children with rates rising sharply after the disappearance of maternally derived antibody. First-generation Hib polysaccharide vaccines often failed when administered during infancy because very young children cannot respond to pure polysaccharides. This problem has been overcome by conjugating the capsular polysaccharide with a protein to create a T cell-dependent antigen to which infants effectively respond. In contrast rubella is primarily a threat to the fetus rather than to infants and young children. The ideal strategy would be to immunize all women of reproductive age before they became pregnant. Because it is difficult to ensure this type of coverage rubella is included in a combination vaccine with measles and mumps MMR that is administered during infancy and boosted at the age of 4-6 years. It is recommended that pregnant women be screened for rubella antibodies and that seronegative women be .