We separate shots, use Benedryl beforehand, always wait at the vet's about
* 45 * minutes afterward, change vaccine type used or drop vaccination for
a given individual animal if there is severe enough a reaction -- depending
on how severe it was, what vet advises, and how common CDV is in the area.
We NEVER give a vaccine type which caused a severe reaction to that
individual again.  In a very extreme reaction do not be surprised if the
ferret needs antihistamines, epinephrine, steroids, fluids, oxygen, etc.
Have also had two (related to each other) who couldn't cope with rabies
vaccine over the 18 years or so that we've shared lives with them; that
apparently is much more rare and almost never hear of that happening.
Yes, bloody runs can happen as part of the reaction and antibiotics are
sometimes given to prevent a secondary reaction.  Replacing beneficial
intestinal bacteria can make sense, too.
 
Anaphylactic reactions are by definition typically life-threatening.  It's
basically the same sort of reaction you read about killing people who are
allergic to penicillin, or bee stings, or certain foods, or... There are
more extreme responses sometimes given for humans who have such reactions,
but when one gets that much more extreme brain damage can occur and death
can be preferable for some depending on the type of brain damage.
 
Allergies can develop at any point in life; they require previous exposures
to the allergan (or something closely related when there has been
generalization) since the body has to have "decided" to mis-recognize the
item as a serious illness which must be fought in a strong fashion.  That
combative mode can become so extreme that the reaction itself can kill
(with asthma, anaphylatic reaction, dermal necrosis...).  In fact, it's
usually the things to which individuals have the most exposure that a
reaction is likely to develop -- most commonly eaten foods, favorite foods,
etc.  (There's a lot to be said for variety.)
 
There is a new Merial Recombitek CDV vaccine under testing now which so far
has caused NO reactions.  Fortunately, only a small percentage of ferrets
have vaccine reactions, but it has happened for some with each of the two
types commonly given, so precautions must always be taken.
 
Am breathing today!  Yippee!  (Hoping for more cleaned-out air with low
enough rag weed pollen...)
[Posted in FML issue 3166]