Continuous Monitoring for Safety

Once on the market, samples of every new lot of vaccine must be submitted to the FDA before it is sold. This ensures that each batch is as safe and effective as the last. Continuous monitoring of vaccines being administered ensures that each dose of the vaccine remains safe and effective, tracking any side-effects from the vaccine and responding to any potential safety issues.

  • The Center for Biologics Evaluation and Research (CBER) at the United States Food and Drug Administration (FDA) receives the results of key tests, along with samples of the product, sent by manufacturers who must continually test and submit their products for evaluation before the CBER will approve the release of that lot of vaccine for administration. Tests performed on the final product may include those for sterility, identity, purity, and potency to assess immunogenicity (the ability to produce an immune response) and/or immunological content, among others. The Vaccines and Related Biological Products Advisory Committee reviews and evaluates data concerning the safety, effectiveness, and appropriate use of vaccines, reporting regularly to the FDA.

  • The Vaccine Safety Datalink (VSD) has collected statistics from more than 7 million people in major health plans who have received vaccines since 1990. The VSD was developed to monitor immunization safety and address the gaps in scientific knowledge about rare and serious events following immunization. The VSD has proven to be a highly effective tool for evaluating immunization safety, publishing numerous scientific studies on the best ways to use existing immunization safety data. The VSD has conducted a variety of analysis including:

    • A study that compares the risk of febrile seizures in children who receive MMRV vaccine versus children who receive MMR and varicella vaccine separately.

    • An evaluation of the VSD data to examine the safety of thimerosal-containing vaccines.

    • An evaluation of the risk of intussusceptions following rotavirus vaccine (which was essential in the eventual withdrawal of the vaccine from the market due to confirmed link to intussusceptions).

    • Active surveillance of 2009 H1N1 influenza vaccine which provided real-time data to public health official tasked with ensuring the safe vaccination of the population.


  • The Vaccine Adverse Event Reporting System (VAERS) gathers information about any side effects patients have experienced from vaccines. Medical personnel are required by law to report any adverse events to the system, however reports may be submitted by any individual. The system was developed in 1990 by the CDC and the FDA. In 1999 the VAERS system detected that infants receiving Rotashield rotavirus vaccine were at increased risk for intussusception following vaccination. The vaccine was temporarily halted until epidemiological studies could be conducted; these studies confirmed the VAERS results and the vaccine was permanently removed from the market. A new vaccine was later developed, which has saved the lives of millions of children worldwide with no reported issues.

  • The Clinical Immunization Safety Assessment (CISA) Network is a national network of six medical research centers with expertise in immunization safety conducting clinical research on immunization associated health risks. CISA was established in 2001 as a collaborative project between the Immunization Safety Office, six medical research centers, and America's Health Insurance Plans.

    Experts in vaccinology and vaccine safety from the six academic medical centers convene a monthly conference call, during which a complex vaccine safety issue is addressed in a structured format. An investigator presents a case, which includes the history of present illness (the adverse event reported following vaccination), and detailed physical and diagnostic (laboratory and other) findings. A summary of a literature review on this subject and the Vaccine Adverse Event Reporting System (VAERS) data are also presented. The experts discuss the findings and formulate a general assessment and plan. When appropriate, these conclusions are shared with the concerned provider.

  • The Brighton Collaboration is an international voluntary collaboration that aims to enhance the science of vaccine research by providing standardized, validated, and objective methods for monitoring safety profiles and benefit to risk ratios of vaccines. This objective group of scientists from around the globe are committed to ensuring that the world has the safest, most effective vaccines available based on rigorous science.


The National Vaccine Injury Compensation Program (NVICP)
Although severe adverse events are rare, the NVICP was created to compensate people who may have been injured by vaccines. More information on this program including how to file a claim is available on the NVICP website.

Additional Resources


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