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bullet Vaccine Safety Datalink (VSD) Project
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Vaccine Safety Datalink (VSD) Project

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The Vaccine Safety Datalink (VSD) project is a collaborative effort between CDC's Immunization Safety Office and eight large managed care organizations (MCO). The VSD project was established in 1990 to monitor immunization safety and address the gaps in scientific knowledge about rare and serious adverse events following immunization.

The VSD project includes a large linked database that uses administrative data sources at each MCO. Each participating site gathers data on vaccination (vaccine type, date of vaccination, concurrent vaccinations), medical outcomes (outpatient visits, inpatient visits, urgent care visits), birth data, and census data.

The VSD project allows for planned immunization safety studies as well as timely investigations of hypotheses that arise from review of medical literature, reports to the Vaccine Adverse Event Reporting System (VAERS), changes in immunization schedules, or the introduction of new vaccines.

Since 1990, investigators from the VSD project have published more than 75 scientific articles. The VSD project has addressed the following immunization safety concerns:

  • A study that quantifies the risk of seizures after receipt of whole-cell pertussis or measles, mumps, and rubella (MMR) vaccine
  • An investigation of MMR and other measles-containing vaccines, which found no increased risk for inflammatory bowel disease
  • An examination of the safety of revaccination with the pneumococcal polysaccharide vaccine
  • An evaluation of the VSD data to examine the safety of thimerosal-containing vaccines

The VSD project has proven to be a highly effective tool for evaluating immunization safety.


Managed Care Organization Sites

Map of the United States showing the locations of the eight managed care organization sites. All of the sites serve all ages except HealthPartners Research Foundation and Marshfield Clinic Research Foundation, which serve only those aged less than 18 years.

  • Group Health Cooperative of Puget Sound, Seattle, WA
  • Kaiser Permanente Northwest, Portland, OR
  • Kaiser Permanente Medical Care Program of Northern California, Oakland, CA
  • Southern California Kaiser Permanente Health Care Program, Los Angeles, CA
  • HealthPartners Research Foundation, Minneapolis, MN
  • Marshfield Clinic Research Foundation, Marshfield, WI
  • Kaiser Permanente Colorado, Denver, CO
  • Harvard Pilgrim Health Care, Boston, MA


  • To conduct population-based research on immunization safety questions
  • To evaluate immunization safety hypotheses that arise from medical literature, passive surveillance systems, adjustments to immunization schedules, and introduction of new vaccines
  • To guide national immunization policy decisions
  • To partner with healthcare providers, public health officials, and others to ensure the public has the best available information regarding the risks and benefits of immunizations

Priority Studies

Rapid Cycle Analysis (RCA)

Rapid Cycle Analysis (RCA) is an active surveillance system designed to detect adverse events (possible side effects) following vaccination in near real time, so the public can be informed quickly of possible risks.

Read the VSD 2004–2005 Annual Report.*

*Links to non-Federal organizations found at this site are provided solely as a service to our users. These links do not constitute an endorsement of these organizations or their programs by CDC or the Federal Government, and none should be inferred. CDC is not responsible for the content of the individual organization Web pages found at these links.

Page last reviewed: September 24, 2008
Page last updated: October 27, 2008
Content source: Immunization Safety Office

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