Extraimmunization among US children

Context Little is known about the extent of extraimmunization, ie, vaccine doses given in excess of the recommended, schedule, and whether it should b e a public health concern. Objectives To determine the extent and cost of extraimmunization in childre n and to identify its associated factors. Design, Setting, and Participants United States 1997 National Immunization Survey, in which telephone interviews were conducted with parents of 32 742 19- to 35-month-old children and vaccination histories were collected from health care providers for 22 806 of these children (overall response rate, 68.5%). Estimates were weighted to represent the full sample. Main outcome Measures Frequency of extraimmunization compared by vaccine ty pe as well as with adequate immunization; factors associated with extraimmu nization; and vaccine and visit costs associated with extraimmunization. Results Frequency of extraimmunization was less than 5% for each vaccine co nsidered except poliovirus (14.1%). Overall, 21 % of children were extraimm unized for at least 1 vaccine vs 31 % underimmunized for at least 1 vaccine . in a multivariate model, the strongest contributors to extraimmunization were having more than 1 immunization provider (odds ratio [OR], 2.8; 95% co nfidence interval [CI], 2.4-3.2) and having multiple types of providers (eg , private and public health department, OR, 2.0; 95% CI, 1.6-2.4). Children seen only in public health department clinics were significantly less like ly to be extraimmunized (OR, 0.3; 95% CI, 0.2-0.3). Annual costs associated with extraimmunization for this cohort of children were estimated conserva tively at $26.5 million. Conclusions These data indicate that extraimmunization can be costly, The c hallenge is to reduce extraimmunization without interfering with more impor tant efforts to combat underimmunization. Improvements in immunization reco rd keeping and sharing practices may help reduce extraimmunization.