Monitoring the impact of human papillomavirus vaccines on high-grade pre-invasive cervical lesions: designing a framework of linked immunization information system and cancer registry data in Michigan.

State immunization and cancer registries contain data that, if linked, could be used to monitor the impact of human papillomavirus (HPV) vaccine on cervical cancer and precancer. Michigan is uniquely positioned to examine these outcomes using two population-based resources: the state-wide cancer registry and immunization information system (IIS). We assessed the feasibility of identifying females in the IIS who had continuous Michigan residence and linking them to the cancer registry. We considered continuous residence necessary for future studies of vaccine impact to avoid misclassifying those who may have been immunized while residing out-of-state and whose immunization therefore may not have been reported in Michigan. We identified females with 1976-1996 birthdates in the IIS and used probabilistic linkage software to match them with Michigan birth records. A stratified random sample of IIS-birth matches was provided to a commercial locator service to identify females with continuous Michigan residence. Cervical carcinoma in situ cases diagnosed in 2006 among females aged 10 through 30 years were also matched with the birth records; cancer registry-birth matches were merged with the IIS-birth matches using the birth record identifier. Overall, 68% of the 1274,282 IIS and 61% of the 1358 cancer registry records could be matched with birth records. Among the sample of IIS-birth matches, most (86%) were continuous residents. Seventy percent or more of cancer registry-birth matches merged with IIS-birth matches for cases born after 1984. This is the first effort in the U.S. to show that linking records across IIS and cancer registries is practical and reasonably efficient. The increasing proportion of matches between the registries and live birth file with birth year, and the use of population-based data, strengthen the utility of this approach. Future steps include use of this method to examine incidence of cervical cancer precursors in HPV immunization-eligible females.