VAERS accepts reports of adverse events and reactions that occur following vaccination. Healthcare providers, vaccine manufacturers, and the public can submit reports to the system. While very important in monitoring vaccine safety, VAERS reports alone cannot be used to determine if a vaccine caused or contributed to an adverse event or illness. The reports may contain information that is incomplete, inaccurate, coincidental, or unverifiable. In large part, reports to VAERS are voluntary, which means they are subject to biases. This creates specific limitations on how the data can be used scientifically. Data from VAERS reports should always be interpreted with these limitations in mind.
The strengths of VAERS are that it is national in scope and can quickly provide an early warning of a safety problem with a vaccine. As part of CDC and FDA’s multi-system approach to post-licensure vaccine safety monitoring, VAERS is designed to rapidly detect unusual or unexpected patterns of adverse events, also known as “safety signals.” If a safety signal is found in VAERS, further studies can be done in safety systems such as the CDC’s Vaccine Safety Datalink (VSD) or the Clinical Immunization Safety Assessment (CISA) project. These systems do not have the same scientific limitations as VAERS, and can better assess health risks and possible connections between adverse events and a vaccine.
Key considerations and limitations of VAERS data:
VAERS data available to the public include only the initial report data to VAERS. Updated data which contains data from medical records and corrections reported during follow up are used by the government for analysis. However, for numerous reasons including data consistency, these amended data are not available to the public.
Yes. The lion’s share of the drop was caused by the removal of the free text field in the European data (read here for a fuller explanation of this).
However, the removal of the European free text field data last month precipitated our reevaluating our myocarditis query. Last September we had launched a revamped backend engine to our site, in the process rewriting the more complicated queries to optimize for efficiency. When checking over things recently we found that our query for myocarditis needed revision (mostly due to it having an overly broad search term-the result of trying to simplify code). We are currently checking all our non-boolean queries-and likely a few more will be revised (some up, some down). Once done, we will work on open sourcing our queries to the public and possibly adding a changelog.
It is important to keep in mind that OpenVAERS is continually updating its programming -- that's the nature of what we do. Once the queries are made public it will be possible to provide feedback on them.