摘要：Objectives. We have described vaccine coverage of Michigan young adolescents immunized with tetanus, diphtheria, and pertussis; meningococcal conjugate; and human papillomavirus vaccines during 2006–2008. Methods. We obtained data from the Michigan Care Improvement Registry, a state-based immunization information system that included more than 57 million vaccination records. We examined 3 overlapping cohorts of 11- and 12-year-old children (n > 350 000 in each) to assess temporal trends in vaccination coverage, characteristics of those immunized, funding sources, and vaccination sites. Results. Vaccine uptake increased during 2006 through 2008, peaking in the summer months. More than half of children receiving more than 1 vaccine received the vaccines simultaneously. Older age, receipt of Medicaid, and prior completion of early childhood immunizations were associated with greater odds of vaccination. Conclusions. Vaccine coverage among Michigan young adolescents is increasing but continues to be relatively low. Coverage of 11- and 12-year-old children may improve with efforts to encourage vaccination at all health care visits, an increase in public funding in support of adolescent vaccination, and continued monitoring of adolescent vaccination levels through school-based assessments. Vaccinations have been hailed as among the “ten great public health achievements of the twentieth century” 1 and have had a major impact on improving the health of children and adults. The development and utilization of vaccines are generally considered among the most cost-effective and successful public health interventions to prevent and control infectious diseases. 2 Despite dramatic reductions, vaccine-preventable diseases continue to pose a health threat, and concerns over vaccine safety create an ongoing challenge for public health officials and immunization programs. Paradoxically, the historically low rates of many vaccine-preventable diseases make rare vaccine-related adverse events disproportionately prominent to the point that some individuals perceive the risks of vaccine side effects to be greater than those of the disease itself. 3 Compounding these issues is the expanding number of recommended vaccines owing to the licensure of new vaccines and the addition of doses of existing vaccines. 4 For example, the Advisory Committee on Immunization Practices (ACIP) recommended 3 relatively new vaccines for preadolescents: the tetravalent meningococcal conjugate vaccine (MCV4) starting in 2005; the new vaccine formulation including tetanus, diphtheria, and acellular pertussis (Tdap) components, which differs from the DTaP (diphtheria, tetanus, and pertussis) vaccine, beginning in 2006; and 3 doses of human papillomavirus vaccine (HPV) for girls since 2007 and boys since 2009. 4 Although some of these vaccines can be given earlier, most are given when children are aged 11 or 12 years. 5 Administration of these vaccines at the same health care visit is recommended to capitalize on the opportunity at hand, 6 as simultaneous administration of vaccines produces seroconversion rates similar to those when given separately. 5,7,8 Although prevention of illness in infants and young children has been a focus of immunization programs, adolescents also have a higher burden of vaccine-preventable diseases, such as pertussis, than do older age groups 9 and a higher incidence of meningococcal disease than does the general population, 10 reinforcing the need to understand vaccination trends in this age group. Young adolescents are considered an especially hard-to-reach population because they have fewer visits to health care providers and, therefore, a greater likelihood of missed opportunities for vaccination. 11 Immunization coverage is likely lower in adolescents, but we lack a good understanding of the contributing reasons. 12 We have described immunization coverage for Tdap, MCV4, and HPV vaccines in Michigan’s 11- to 12-year-old children during 2006, 2007, and 2008. Most prior assessments focused on those aged 13 to 17 years, including a recent study from North Dakota 13 and the National Immunization Survey–Teen (NIS–Teen), 14 and unlike other published adolescent immunization assessments, we used a population-based registry rather than a sample-based survey. The use of data from a state-based immunization information system allows a more comprehensive and accurate description of the characteristics of young adolescents who have received the recommended vaccinations. Understanding factors associated with successful young adolescent immunization may enable health care providers to identify barriers to vaccine uptake and support development of better strategies to improve vaccination coverage in this vulnerable population.
