Hi, Shyla,
 
Please don't worry too much about rocket.  If pretreating with benadryl
doesn't do the trick, your vet can give Rocket a steroid injection that
probably will.  My vet uses dexamethasone in that situation.  The good
news is that of three ferrets who had reactions last year, after
pretreatment none did this year.
 
One other thing: wait *AT LEAST* an hour at the vet after the vaccination.
30 minutes just isn't long enough.  In my Adric's case the reaction
happened a full hour later.
 
All the best,
Caity
[Posted in FML issue 3563]