The FDA (or is it the CDC? Or is it Health & Human Services? Can't really tell....) just updated its Vaccine Adverse Event Reporting System (VAERS)
dataset (April 13, 2009).
What they haven't bothered to note is that they've also changed the
structure of their dataset.
VAERS data
used to come packaged as 2 CSV files--one called
VAERSData.csv and one called
VAERSVaccine.csv.
VAERSData.csv used to contain 20 slots per row for
symptoms associated with each vaccine adverse event.
In the database world, one says that there is a
1-to-many relationship between a VAERS
report and the
Symptoms associated with that report.

And day 1 of any remedial Database management course will inform you that because of the 1-to-many relationship, you should
separate the VAERS record from the Symptoms record
s and link each symptom back to its report via a
foreign key.
The
reason for doing this is that 20 slots for symptoms *may* seem like more than enough slots for any case that you'll ever come across, but at some point, some hypochondriac is going to slip in 21 symptoms and totally screw with your file.
Well, 19 years later, the VAERS folks have finally given the Symptom data its own csv file, appropriately titled
VAERSSymptoms.csv. They didn't bother to
tell anyone that they did this...and
I had to tinker with my parsing algorithm last night to adjust for the changes, but the discerning
pharmacovigilantes among us were able to figure it out when we asked ourselves
"Why are there 3 csv files per year now when there used to be 2? And why haven't they updated their file explaining the structure of the VAERS files?"
As of this writing, the most recent revision of the VAERS explanation is June 2007.
Ah yes...lest I forget...as of this writing, the
Zip file containing all of 2008's VAERS data is contaminated with 2009 data. I think that's just to keep everyone on their toes.