As a starting point, but they use more robust EHR data to actually investigate.
From the very first slide in your link...
>The findings and conclusions in this report are those of the authors
and do not necessarily represent the official position of the Centers
for Disease Control and Prevention (CDC) or the U.S. Food and Drug
Administration (FDA)
Here are the limitations of VAERS as per the CDC.
>Limitations of VAERS:
>It is generally not possible to find out from VAERS data if a vaccine caused the adverse event
>Reports submitted to VAERS often lack details and sometimes contains errors
>Serious adverse events are more likely to be reported than non-serious events
>Numbers of reports may increase in response to media attention and increased public awareness
>VAERS data cannot be used to determine rates of adverse events
FDA and CDC do use VAERS as their source for estimating risk of adverse events:
https://www.cdc.gov/vaccines/acip/meetings/downloads/slides-...
https://www.fda.gov/media/151733/download (page 23)