Impact of the Change to Inactivated Poliovirus Vaccine on the Immunization Status of Young Children in the United States: A Study From Pediatric Research in Office Settings and the National Medical Association James A. Taylor, MD*; Paul M. Darden, MD‡; Dennis A. Brooks, MD, MPH§; J. W. Hendricks, MD; Alison E. Baker, MS¶; Alison B. Bocian, MS¶; Karyn Rohder, BS¶; and Richard C. Wasserman, MD, MPH# ABSTRACT. Objective. To determine whether the change from an all oral poliovirus vaccine (OPV) sched- ule to an inactivated poliovirus vaccine (IPV)-containing schedule has adversely affected the immunization status of young children in the United States. Methods. Immunization data were abstracted from the medical records of children 8 to 35 months old seen consecutively for any reason in the offices of practicing pediatricians who are members of the Pediatric Research in Office Settings network of the American Academy of Pediatrics or the National Medical Association. Data on up to 120 eligible children were collected in each practice between March 1998 and January 2000. Patients were classified as fully immunized at 8 months old if they had received 3 diphtheria-tetanus-pertussis, 2 Haemophilus influenzae type b, 2 hepatitis B, and 2 poliovirus vaccines. Study children who were >12 months of age at the time that data were collected were categorized as being fully immunized at 12 months if they had received the same vaccines before their first birthday. To assess the effect of type of poliovirus vaccines on these outcomes, study patients were classified as being in an IPV or OPV group based on the initial type of vaccine received. Logistic regression was used to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) for IPV as a predictor of being fully immunized at 8 and 12 months of age, after adjusting for race/ethnicity of the patient, maternal edu- cation level, year of birth, and method of payment for vaccines. In addition, the effect of clustering of children within practices was accounted for by the use of gener- alized estimation equation techniques. Results. Data were analyzed on 13 520 children from 177 practices in 42 states; 79.4% of patients were fully immunized at 8 months of age, and 88.7% of those eligi- ble were fully immunized at 12 months of age. A total of 6910 patients (51.1%) were classified as OPV recipients, wheras 5282 (39.1%) received IPV. In addition, 1328 chil- dren (9.8%) were documented as having received polio- virus vaccine, but the particular type could not be deter- mined. Compared with OPV recipients and after controlling for the confounding variables and the effect of clustering within practices, children in the IPV group were as likely as were OPV recipients to be fully immu- nized at 8 months of age (OR: 1.04; 95% CI: 0.88,1.23). At 12 months of age, the OR for IPV as a predictor of being fully immunized was 1.08 (95% CI: 0.90,1.30). When com- pared with OPV recipients, adjusted ORs for children in the undetermined poliovirus vaccine type group being fully immunized at 8 and 12 months of age were 0.84 (95% CI: 0.68,1.04) and 0.84 (95% CI: 0.67,1.07), respec- tively. Conclusions. The results of this national study indi- cate that the implementation of an IPV-containing polio- virus vaccine schedule has not had an adverse effect on the immunization status of young children who were vaccinated in the offices of practicing pediatricians. Pediatrics 2001;107(6). URL: http://www.pediatrics.org/ cgi/content/full/107/6/e90; immunizations, children, polio- virus vaccine. ABBREVIATIONS. IPV, inactivated poliovirus vaccine; OPV, oral poliovirus vaccine; VAPP, vaccine-associated paralytic polio; AAP, American Academy of Pediatrics; HMO, health mainte- nance organization; PROS, Pediatric Research in Office Settings; NMA, National Medical Association; VAR, Vaccine Administra- tion Record; GEE, generalized estimating equation; OR, odds ra- tio; CI, confidence interval; ICC, intraclass correlation coefficient. T he eradication of poliomyelitis in the United States is one of the most gratifying public health achievements of the final half of the 20th century. The last reported indigenous cases of polio- myelitis caused by wild virus in the United States occurred in 1979 1 ; no indigenous cases have been reported in the Western Hemisphere since 1991. 2 This remarkable decline in the incidence of poliomy- elitis is directly attributable to the introduction of inactivated poliovirus vaccine (IPV) in 1955 and oral poliovirus vaccine (OPV) in 1963. 3 Although OPV has been very effective in eliminat- ing wild virus infection, 8 to 9 cases per year of vaccine-associated paralytic polio (VAPP) were re- ported annually between 1980 and 1994. 4,5 Thus, in 1997 the Advisory Committee on Immunization Practices and the American Academy of Pediatrics (AAP) recommended that poliovirus vaccine in the United States be delivered via a sequential IPV/OPV schedule, a change from the all-OPV schedule previ- ously endorsed. 3,6 It was estimated that this change From the *Department of Pediatrics, University of Washington, Seattle, Washington; ‡Department of Pediatrics, Medical University of South Caro- lina, Charleston, South Carolina; §Department of Pediatrics, Johns Hopkins University, Baltimore, Maryland; Pediatric and Adolescent Care, Tulsa, Oklahoma; ¶Division of Primary Care Research, American Academy of Pediatrics, Elk Grove, Illinois; and #Department of Pediatrics, University of Vermont, Burlington, Vermont. Received for publication Oct 18, 2000; accepted Jan 17, 2001. Reprint requests to (J.A.T.) 146 N Canal St, Suite 300, Seattle, WA 98103. E-mail: uncjat@u.washington.edu PEDIATRICS (ISSN 0031 4005). Copyright © 2001 by the American Acad- emy of Pediatrics. http://www.pediatrics.org/cgi/content/full/107/6/e90 PEDIATRICS Vol. 107 No. 6 June 2001 1 of 7 by guest on April 2, 2017 Downloaded from