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In easy-to-understand language
Note: The terms "immunization," "vaccination," and "inoculation" are used to mean essentially the same thing throughout this site.
Key Vaccine Safety Elements
  • The Federal government, including the Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA), as well as vaccine manufacturers continually conduct vaccine safety research and surveillance investigations even after vaccines are licensed for use. The National Vaccine Program Office (NVPO) coordinates federal activities.
  • Vaccine Safety is taken very seriously. The Federal government uses a multi-component system to monitor and assess the safety of vaccines.
    • The Vaccine Adverse Event Reporting System (VAERS), jointly managed by the CDC and FDA, enables parents, health care providers, and manufacturers to report what they believe are adverse events, or reactions to vaccines. Through VAERS, investigators study and evaluate potential links between vaccines and adverse events. Manufacturers are required to report known adverse events to VAERS.
    • The Vaccine Safety Datalink (VSD) Project utilizes vaccine and health data from several health maintenance organizations (HMOs) in order to study signals from VAERS, and explore other vaccine safety research questions regarding any unusual health conditions that may occur around the time of vaccination.
    • The civilian and military sectors are in the process of developing clinical centers to provide close monitoring of those experiencing previous adverse events. The military centers will focus on reactions to the anthrax shot.
    • The Institute of Medicine (IOM) assesses the proper level of public health concern to adverse events and recommends appropriate action, such as surveillance, research, or policy changes.

What is VAERS?

  • VAERS is a tool for monitoring vaccine safety after a vaccine has been licensed for use. Review of VAERS reports can provide additional assurance about vaccine safety, and identify potential problems not observed during pre-licensure clinical trials conducted by vaccine manufacturers because certain adverse events only become apparent when a vaccine is used in a larger population. In the 1990s, 90 percent of reports were non-serious.
  • Anyone can make a report to VAERS, including health professionals, consumers, and manufacturers. To report a health problem following vaccination, a patient, parent, or health care provider can call VAERS at (800) 822-7967 to obtain a reporting form. Forms can also be downloaded from the VAERS website: .
  • Since the system accepts and includes all reports submitted, some events may be due to other unrelated health conditions that occurred around the time of vaccination. In other words, an event that occurs at the time of vaccination is not necessarily caused by the vaccine.
  • A recent example of how VAERS works is the safety evaluation of a new vaccine to prevent a severe diarrheal illness in childhood caused by rotavirus infection. Review of VAERS reports detected a rare health condition that can cause a blockage in the intestines (intussusception). From September 1, 1998 - July 7, 1999, more cases of intussusception following rotavirus vaccine were reported to VAERS than would have been expected. As a result, in July 1999, the CDC recommended postponing administration of the rotavirus vaccine until the association with intussusception could be studied further.
  • Two special studies were then launched by the CDC to study this �signal� from VAERS. Based on these studies, the Advisory Committee on Immunization Practices (ACIP) withdrew its recommendation of rotavirus vaccine in October 1999. This series of investigations demonstrated the unique and vital role the Federal government plays in monitoring vaccine safety to identify and minimize vaccine-related injuries.

What Happens When Rare, Adverse Events are Detected?

  • VAERS reports of life-threatening events, hospitalization and/or extended hospital stay, life-threatening illnesses, disability and all reports of death, are followed up individually by a health professional.
  • Based on careful review, analysis and further investigation of spontaneous reports, FDA can initiate various regulatory actions such as changing vaccine labels or packaging, initiating scientific investigations, distributing safety alerts, inspecting manufacturers� facilities and records, or withdrawing the vaccine from the>
  • The National Vaccine Injury Compensation Program (VICP) is a Federal program that helps children who may have experienced rare, serious vaccine side effects. For details about this program, call (800) 338-2382.
CDC, National Immunization Program:

FDA, Center for Biologics Evaluation and Research:

Last updated: August 2001

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