Some reports to VAERS are studied further in the Clinical Immunization Safety Assessment Network. Among other things, this network aims to “improve the scientific understanding of vaccine safety at the individual patient level” by obtaining and evaluating detailed genetic and other information from each patient (LaRussa et al., 2011).

Electronic Medical Records

For 2011, it is estimated that 57 percent of office-based physicians used electronic medical records (EMRs), up from 24 percent in 2005 (Hsiao et al., 2011). The EMRs most useful for medical research are the ones from large health plans, as they contain medical records for a well-defined member population, including both inpatient and outpatient encounters. The VSD project is the premier EMR-based vaccine safety system in the United States (Baggs et al., 2011; Chen et al., 1997; DeStefano and the Vaccine Safety Datalink Research Group, 2001). Led by CDC, it is a collaboration with 10 health plans: Group Health in the State of Washington; Harvard Pilgrim/Atrius Health in Massachusetts; HealthPartners in Minnesota; Kaiser Permanente in Colorado, Georgia, Hawaii, Northern California, Oregon, and Southern California; and Marshfield Clinic in Wisconsin. Together, these health plans have about 9.5 million members and an annual birth cohort of more than 100,000. The VSD system is used both for retrospective studies and for near-real-time vaccine safety surveillance with weekly analyses of newly approved vaccines. Similar systems exist in a few other countries, including the Epidemiology Vaccine Research Program at the National Institute for Health Data and Disease Control (Statens Serum Institut) in Denmark.

The major advantage with EMR systems is that denominator data are available, as all vaccinated children can be identified. It is then possible to compare the number of adverse events in vaccinated and unvaccinated children or vaccine-exposed and unexposed time periods within the same child. A disadvantage is that the data are registered for purposes other than research, and there is sometimes miscoding of health events. Depending on the health outcome, manual chart review is therefore sometimes warranted.

Health Insurance Claims Data

Health insurance companies have medical information for millions of insured members and their families, which they receive when doctors and hospitals file their financial reimbursement claims. One such system in the United States is the PRISM program, run by FDA as part of its Mini-Sentinel project (Nguyen et al., 2012). Claims data are more limited than EMRs but can be used in much the same way for postmarketing vaccine



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