Definitions:

​Vic PDC: Whether or not the mother has received an influenza vaccine during the prenancy.
NPDC, WA PDC: The trimester of this pregnancy in which this woman received vaccination against influenza (Vaccinated during first trimester; Vaccinated during second trimester; Vaccinated during third trimester; Vaccinated in unknown trimester; Not vaccinated; Unknown if vaccinated).
Qld PDC: An indicator Yes/No for whether a vaccination for influenza was received during this pregnancy. If yes, at what gestation was this vaccination received(completed weeks).