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Symptoms (Expert Mode)

When in Expert Mode (the checkbox in the upper-right corner) there are many more choices for how symptoms are handled. The VAERS database uses the MedDRA symptom classification, and in Expert Mode, it is possible to explore the MedDRA hierarchy in both case choosing and presentations.


The Medical Dictionary for Regulatory Activities (MedDRA) is a five-level orgnization of all known symptoms:

Although the full hierarchy is propreitary information, MedAlerts offers a reduced MedDRA that includes only those terms found in VAERS data.

Symptoms in VAERS are expressed in Lower-Level Terms. Therefore, when grouping (for Tables and Graphs) or when selecting symptoms in Section 2, these Lower-Level Terms are used.

In Expert Mode, it is possible to look at higher levels of the symptom hierarchy for the purposes of presentations or choosing cases. For example, if you want to see all VAERS cases that have heart-related symptoms, you can set the MedDRA Level (in Section 2) to SOC and then select the "Cardiac disorders" symptom. Similarly, if you want to show a table of the broadest symptom classes, you could make a table of Symptoms SOC (Highest).

Standardized MedDRA Queries (SMQs)

Another part of the MedDRA, which is available only in Expert Mode, is the ability to work with Standardized MedDRA Queries (SMQs). These are groups of Lower-Level Terms that have been deemed (by teams of physicians) to be part of "standard" medical concepts. Symptoms in a SMQ are defined as either "narrow" (symptoms that strongly indicate the SMQ) or "broad" (symptoms that may help to identify the SMQ but do not necessarily indicate the condition). There are only about 200 SMQs, which is far fewer than the number of symptoms in the MedDRA.

For example, the Dementia SMQ has 110 narrow symptoms and 485 broad symptoms. This means that any of the 110 narrow symptoms (Creutzfeld-Jacob disease, Korsakov's syndrome, Senility, etc.) will strongly suggest that the patient has dementia, whereas the 485 broad symptoms could indicate dementia, but not necessarily.

You can search for all VAERS cases that match a SMQ (either broadly or narrowly). Similarly, you can make tables or graphs of the SMQs (either broadly or narrowly) from your search results.

It makes no sense to choose both a SMQ and a symptom term, because the search engine finds cases that match ALL requests. Therefore, if you choose a SMQ (which implies a particular set of symptom terms) and you also choose a symptom term, then only cases that satisfy both requests will be selected. If the chosen symptom term is not in the SMQ's list, then no VAERS cases will be found, whereas if the chosen symptom term is in the SMQ's list, then the selection of the SMQ is effectively ignored.

The Symptom Tree is not a Tree

One of the confusing aspects of the MedDRA is that it appears to have a tree-like structure, with each level of the hierarchy branching out to lower levels. However, the lower levels of the hierarchy often share symptom terms.

For example, the HLGT called "Administration site reactions" falls under two different SOC terms: "General disorders" and "Injury". Therefore, every symptom that appears below "Administration site reactions" actually appears twice in the symptom hierarchy. Also, the PT "Injection site joint pain" comes from two different HLTs, and one of those appears in two different SOCs, causing "Injection site joint pain" to appear three times in the MedDRA.

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