As of October 2004, the NIP had received proposals requesting the use of VSD data from a very small number of researchers. In September 2002, the NIP received proposals from one group of researchers for 13 new vaccine safety studies and 11 reanalyses (CDC, 2004d). Those proposals were revised and slightly modified. The first group of researchers visited the National Center for Health Statistics (NCHS) Research Data Center (RDC) in October 2003 and January 2004 (Geier and Geier, 2004) to analyze the VSD data for which their access was approved. In August 2003, the NIP received a proposal from another researcher for a reanalysis of a published VSD study of the association between measles-mumps-rubella and varicella vaccines and type 1 diabetes (CDC, 2004f). The researcher’s proposal was complete, but at the time of this writing the researcher had not pursued the next steps in the process.
CDC experienced several challenges in implementing the VSD data sharing program. At the time of the announcement of the data sharing program, CDC did not have a formal data sharing policy to provide a standard or guide for the VSD program (Wharton, 2004). Congressional interest in the status of the VSD data sharing program brought increased scrutiny and time pressures to the development process. Analytic data files from some previously published VSD studies had not been archived in a standard manner, so it was difficult to respond expeditiously to requests to reanalyze published VSD studies. The scope of the data sharing program also had to satisfy the dual objectives of providing access to VSD data and ensuring the privacy of the personal medical information in the VSD (Wharton, 2004). NIP resources and personnel were challenged by those events and competing demands and by the adversarial environment that soon emerged.
Four successive versions of the VSD data sharing program guidelines for independent external researchers have been released publicly. Each version of the guidelines was intended to provide greater clarification about program requirements and expectations than the version before it. In August 2002, the first version of Guidelines for Data Sharing Proposals from External Researchers: Vaccine Safety Datalink (VSD) Project was released (CDC, 2002). The guidelines outlined the process for submitting proposals to the NIP, the suggested proposal elements, and the process for re-