>We decided to switch from Fervac to Galaxy-D after reports that there is
>a small chance Fervac can actually *give* distemper, and because Galaxy-D
>is supposed to be *less* likely to cause a reaction.
 
There is a small chance that any vaccine which is a modified live vaccine
(a weakened form of the virus) can actually cause the disease it's intended
to prevent.  However they are more likely to *prevent* the disease than a
killed virus, so out of a group of animals given one or the other you wind
up with less animals getting the disease from the modified live than
getting it because they weren't protected in the first place.
 
Both Fervac and Galaxy-D are modified live.  I doubt there is any
significant difference in risk of causing the disease between the two.
 
I've read (don't remember if it was here or not) that switching between the
two may cause a reaction.  (I don't remember if it mattered which direction
the switch went in, but I think the info was from the mfr, United Vaccine,
so you may want to have your vet check with them.)
 
-Ilena Ayala
[Posted in FML issue 2458]