Orac gives a fine example of what "dumpster-diving" in VAERS entails

What it is, in actuality, is yet another example of the Geiers [http://www.jpands.org/vol11no1/geier.pdf - his paper purports to show that autism rates had started to dip since early 2003, when the last lots of thimerosal-containing childhood vaccines expired] mining the Vaccine Adverse Events Reporting System (VAERS) database for purposes for which it was never designed and misusing the California Department of Developmental Services (CDDS) database similarly. First, off, as I pointed out extensively before, the VAERS database is designed only as an early warning system for reporting adverse events thought to be due to vaccines. It is not designed to track the incidence or prevalence of vaccine complications. One reason is that anyone can make entries into it, not just medical professionals, and the results are only checked in the most perfunctory way.,,, Worse, as I described before, the database has been corrupted by litigation, with a dramatic increase of entries linked to litigation claiming that thimerosal caused the plaintiff’s child’s autism.

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The bottom line is that the VAERS database is not a reliable source to determine autism prevalence or incidence, period. It’s too prone to being affected by scares, like the recent hype over mercury supposedly causing autism, and even outright manipulation, and its entries aren’t even examined by medical professionals in sufficient detail to determine whether adverse events reported were or could be reasonably inferred to have resulted from vaccines. Of course, that never stopped the Geiers from diving into that database again and again and again, all without acknowledging the shortcomings of this database. And it actually wouldn’t be all too surprising if reports of autism attributed to vaccines in the VAERS database did indeed fall after 2003, given that it was widely publicized that thimerosal was removed from nearly all childhood vaccines around that time, making it less likely after then that parents would attribute their children’s autism to vaccines.

The Geiers go dumpster-diving yet again