Each month, the U.S. Government publishes a new version of its VAERS database. Most of the differences between versions consist of new VAERS events that were introduced since the previous version. But the government never closes a VAERS event, and may make changes to any event at any time. Sometimes events are even deleted.

The VAERS Wayback Machine has a collection of old versions of the VAERS database, starting in 2003. It allows you to examine the government data more carefully and observe how the data changes over time. Here are some of the things that you can do with the VAERS Wayback Machine:

Enter a VAERS ID number here to see all changes that have been made to that event since it was first published. You can find out when the event first appeared, how it was modified, and if applicable, when it was deleted. See the How Differences are Shown section below for more about interpreting the results.

Select two different VAERS versions to compare them. All VAERS events that are found in both versions will be examined and the differences described. See the How Differences are Shown section below for more about interpreting the results.

Select two different VAERS versions to compare them. All VAERS events that are in just one of the two versions will be listed.

Do a search of an older VAERS database.

Here is a sample event showing differences. Note the use of color coding: Red indicates something that was in the older version and is therefore removed. Green indicates something that is in the newer version and is therefore added.

In the sample event below (a fictitious event), the date of vaccination and onset has changed; the manufacturer of the Flu vaccine has changed, number of days in the hospital was entered (was previously blank), symptoms have changed (four of them have been removed), and the write-up and preexisting conditions were edited.

Differences between 8/31/2010 and 10/5/2010:

VAERS ID: 274544/274544   Vaccinated: 2005-11-29/2006-11-30 Age: 1.0   Onset: 2005-11-29/2006-11-30 Gender: Male   Submitted: 2006-12-04 Location: Louisiana   Entered: 2006-12-04	Life Threatening Illness? Died? Disability? Recovered? Yes ER or Doctor Visit? Hospitalized? Yes, days: (blank)/1     Extended hospital stay? Current Illness: Diagnostic Lab Data: Previous Vaccinations: Other Medications: J-tan 2ml twice a day Preexisting Conditions: SGA, Hemangioma, Chiritis/Rhinitis, Term baby CDC 'Split Type':
Vaccination Manufacturer Lot Dose Route Site FLU: INFLUENZA (SEASONAL) (FLUZONE) AVENTIS PASTEUR/SANOFI PASTEUR U2174KA 0 IM LL HEPA: HEP A (HAVRIX) MERCK & CO. INC. 0560R 0 IM RL
Administered by: Public     Purchased by: Public Symptoms: Anaphylactic reaction, Angioneurotic oedema, Dyspnoea, Eye swelling, Swelling face, Vaccination complication, Wheezing Write-up:Administration to a child <4 yold. Initial case report received from a pediatrician via agency on 04 NOV 2009. A 1-year-old male patient was accidentally vaccinated with FLUVIRIN 2009/2010 i.m. on 30 OCT 2009. No adverse effect was reported. Company assessment: Seriousness criterion: not serious. Causality: not applicable. No measures necessary.