Vaccine Adverse Event Reporting System (VAERS)

Who, What, When, Were and Why

Researchers can get lazy and start to use acronyms and initializations to save time and keystrokes. Apparently I have been guilty of using such abbreviations, without proper explanation.

Recently a reader sent an email asking me just what is VAERS anyway, who runs it, what information are they tracking, how do the get it and from whom. Rather that give my Inconvenient Woman readers a two second summary, back to saving keystrokes again, I ‘m using the VAERS description copy directly from the CDC site. That way I wont miss any of the important stuff, trying to save keystrokes. (Editorial note: I’m not a touch typist. Typing class was taught at the same time as Latin, and for reasons that escape me now, I chose conjugation of Latin verbs over a useful life skill.)

Vaccine Adverse Event Reporting System (VAERS)

Photo of Mother Holding Baby

Vaccines are developed in accordance with the highest standards of safety. However, as with any medical procedure, vaccination has some risks. Individuals react differently to vaccines, and there is no way to predict the reaction of a specific individual to a particular vaccine.

The National Childhood Vaccine Injury Act (NCVIA) requires health care providers to report adverse events (possible side effects) that occur following vaccination, so the Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) established the Vaccine Adverse Event Reporting System (VAERS) in 1990. VAERS is a national passive reporting system that accepts reports from the public on adverse events associated with vaccines licensed in the United States. VAERS data are monitored to—

  • Detect new, unusual, or rare vaccine adverse events
  • Monitor increases in known adverse events
  • Identify potential patient risk factors for particular types of adverse events
  • Identify vaccine lots with increased numbers or types of reported adverse events
  • Assess the safety of newly licensed vaccines

Approximately 30,000 VAERS reports are filed annually, with 10–15% classified as serious (causing disability, hospitalization, life-threatening illness or death). Anyone can file a VAERS report, including health care providers, manufacturers, and vaccine recipients or their parents or guardians. The VAERS form requests the following information: the type of vaccine received, the timing of vaccination, the onset of the adverse event, current illnesses or medication, past history of adverse events following vaccination, and demographic information about the recipient. VAERS forms can be completed online, or you can complete a paper form and mail or fax it to VAERS. To request a paper VAERS form to be faxed to you, or if you need assistance in filling it out, call (800) 822-7967.

A contractor, under the supervision of FDA and CDC, enters the information from VAERS forms into a database. Those reporting an adverse event to VAERS receive a confirmation letter containing a VAERS identification number. Additional information may be submitted to VAERS using the assigned identification number. Selected cases of serious adverse reactions are followed up at 60 days and one year post-vaccination to check the recovery status of the patient. The FDA and CDC use VAERS data to monitor vaccine safety and conduct research studies. VAERS data (without identifying personal information) are also available to the public.

While VAERS provides useful information on vaccine safety, the data are somewhat limited. Specifically, judgments about causality (whether the vaccine was truly responsible for an adverse event) cannot be made from VAERS reports because of incomplete information. As a result, researchers have turned more recently to large-linked databases (LLDB) to study vaccine safety. LLDB provide scientists with access to the complete medical records of millions of individuals receiving vaccines (all identifying information is deleted to protect the confidentiality of the patient). One example of a LLDB is the Vaccine Safety Datalink (VSD) Project.

Reporting Vaccine Adverse Events

Everyone is encouraged to report any clinically significant or unexpected event (even if uncertain that the vaccine caused the event) for any vaccine. The Reportable Events Table (RET) lists and explains injuries and conditions that are presumed to be caused by vaccines, and time periods in which the first symptom must occur after receiving the vaccine. It is used by the Vaccine Injury Compensation Program, which is operated by the U.S. Health Resources and Services Administration. Health care providers are required by law to report to VAERS any conditions on the RET, vaccine adverse events that are listed in the manufacturer’s insert, and clinically significant or unexpected events following vaccination.

National Surveillance Data for Vaccine Adverse Events

VAERS Data: When evaluating data from VAERS, it is important to note that for any reported event, no cause-and-effect relationship has been established. VAERS receives reports on all potential associations between vaccines and adverse events. Therefore, VAERS collects data on any adverse event following vaccination, be it coincidental or truly caused by a vaccine. The report of an adverse event to VAERS is not documentation that a vaccine caused the event.

Recent Research

In 2006, FDA licensed RotaTeq, a new rotavirus vaccine. The same year, CDC implemented a post-licensure vaccine safety study of the RotaTeq vaccine.

Other Resources

VAERS Brochure

Scientific Articles

  1. Varricchio F, Iskander J, Destefano F, Ball R, Pless R, Braun MM, Chen RT. Understanding vaccine safety information from the Vaccine Adverse Event Reporting System. Pediatric Infectious Disease Journal 2004;23(4):287–294.
  2. Zhou W, Pool V, Iskander JK, English-Bullard R, Ball R, Wise RP, Haber P, Pless RP, Mootrey G, Ellenberg SS, Braun MM, Chen RT. Surveillance for safety after immunization: Vaccine Adverse Event Reporting System (VAERS)—United States, 1991–2001. MMWR 2003;52(1):1–24.
  3. Chen RT, Rastogi SC, Mullen JR, Hayes SW, Cochi SL, Donlon JA, Wassilak SG. The Vaccine Adverse Event Reporting System (VAERS). Vaccine 1994;12(6):542–550.


PDF IconPlease note: Some of these publications are available for download only as Portable Document Format (PDF) files, which require Adobe® Acrobat® Reader to view. Please review the information on downloading and using Acrobat Reader software.

To download a PDF of VAERS report: Quadrivalent Human Papillomavirus Vaccine (HPV4): Post-licensure Safety Update, Vaccine Adverse Event Reporting System (VAERS), United States Advisory Committee on Immunization Practices, 10-22-08,
Click here


Page last modified: May 12, 2008
Content source: Immunization Safety Office


Author: H. Sandra Chevalier-Batik

I started the Inconvenient Woman Blog in 2007, and am the product of a long line of inconvenient women. The matriarchal line is French-Canadian, Roman Catholic, with a very feisty Irish great-grandmother thrown in for sheer bloody mindedness. I am a research analyst and author who has made her living studying technical data, and developing articles, training materials, books and web content. Tracking through statistical data, and oblique cross-references to find the relevant connections that identifies a problem, or explains a path of action, is my passion. I love clearly delineating the magic questions of knowledge: Who, What, Why, When, Where and for How Much, Paid to Whom. My life lessons: listen carefully, question with boldness, and personally verify the answers. I look at America through the appreciative eyes of an immigrant, and an amateur historian; the popular and political culture is a ceaseless fascination. I have no impressive initials after my name. I’m merely an observer and a chronicler, an inconvenient woman who asks questions, and sometimes encourages others to look at things differently.