Your babies are more likely to have a reaction this time, (and each
subsequent time) than they were during the first series.  It's an allergic
reaction, which is a response to something to which they have been
previously exposed.  Talk to your vet about pre-treating with Pediatric
Benedryl.
 
Personally, we prefer to vaccinate for distemper (Fervac-D) unless a ferret
has had a severe reaction previously, or is in very poor health.  Dr.
Kendrick has us give 1cc Pediatric Benedry an hour before the distemper
vaccine.  This reduced total reactions from 20% to .05%, in 20 vaccinations
of 40 ferrets from the same vaccine lot.  One of the 20% reactions was
critical.  The single reaction from the second group (.05%) was mild
nausea.
 
Debi Christy
Ferrets First Foster Home, Carthage, TX
[Posted in FML issue 2997]