countered include the complexity of the vaccination schedule, the costs of the vaccines, problems with access to health care services, the need for multiple injections at a single visit, lack of parental awareness, competing parental priorities, parental complacency, long waiting times in public clinics, lack of reliable transportation, inappropriate interpretation by physicians and other health care workers of contraindications to immunization, missed opportunities for vaccination (at acute care or emergency room visits), poor record keeping, or the unavailability of records, and concerns regarding adverse reactions to vaccines. The single most important determinant of up-to-date vaccination status by the age of 2 years is the presence of an effective primary care system (Guyer et al., 1994).
Children should receive the majority of the recommended immunizations by age 2. In the 1970s, low rates of immunization among 4- to 6-year-old children who were entering school became a concern. Several efforts contributed to increasing immunization rates to well over 95% among this age group. Specifically, all 50 states instituted the requirement that all children must have received all of the recommended immunizations before entering the public school system. In addition, CDC, AAP, and many nongovernmental community-based organizations undertook major efforts to improve immunization rates.
In the 1990s, concern shifted to improving immunization rates among preschool-age children. Coverage rates for some specific vaccines have now risen to over 90% for 2-year-olds, but rates of completion of the full set of recommended immunizations remain below 80% (CDC, 1998). A number of imaginative programs have been undertaken to improve this rate of coverage. Some of the steps include opening public health clinics in the evening and on Saturdays to accommodate families in which both parents are employed or to accommodate single-parent families. Immunization clinics have been established in or near the offices of various federal entitlement programs such as those for the Aid to Families with Dependent Children program and the Supplemental Food Program for Women, Infants and Children. The requirement that an immunization visit include a full health examination has been abandoned in public clinics. Illinois established a program that provided public clinics with a $10 bonus for each child who was up-to-date on the recommended schedule by age 2 years and a $15 bonus for each child if the overall rate of immunization coverage at the clinics was greater than 85%. With this type of stimulation, coverage rates in Illinois have improved markedly (from 75% to 89%) despite the introduction of new vaccines that have further complicated the immunization schedules. Finally, to help make the receipt of multiple immunizations more convenient, some public schools have incorporated immunizations into their school health programs so that preschool-age infants and children may attend neighborhood-school health clinics where school health nurses or other personnel immunize younger cohorts who are not yet attending school.
In attempts to reduce the numbers of required injections, pharmaceutical firms have accelerated R&D on products that combine multiple antigens (diphtheria and tetanus toxoids and acellular pertussis vaccine plus Hib, Hib plus