There are many reasons why a dog has an adverse reaction to a vaccine. Sometimes it's not even the vaccine itself that they have the reaction, but the adjuvant, which is an ingredient that is added to the vaccine to improve the immune response. Aluminum hydroxide is a common vaccine adjuvant, yet sometimes certain animals just have a problem with it. Aluminum hydroxide is also the adjuvant that has been implicated in causing cancerous injection site tumors, which is why vaccine protocols have been changed to injecting the animals in the leg instead of in the hip or in the scruff of the neck. This way, if a cancerous tumor does develop, the leg can be amputated to save the life of the animal, whereas if it was in the hip or the scruff of the neck, obviously amputation would be impossible.
Some rabies vaccines are modified live vaccines, which means that the vaccine itself is live, but modifications have been made to make it a non-disease-causing version of the virus. Some are killed vaccines, which means that the vaccine is not alive. It could be that it was the type of vaccine that was given to your Chi that caused the reaction and not the adjuvant. It is difficult to say whether it was the vaccine itself or the adjuvant that caused the anaphylaxis, but in animals such as yours, further vaccinations are not advisable just to be on the safe side. It's not worth taking chances.
If your pet is an indoor-only pet, this isn't a problem with rabies vaccines, since there is no danger of rabies if the animal is always in the house and is supervised on its visits to the outdoors to go to the toilet. Of course, there is always a remote chance that a bat could find its way into your house via a chimney or other means, but it's not enough of a chance to risk your pet's life to vaccinate it when it is known that the vaccine is problematic for the pet. Where you MIGHT run into a problem, however, is if you ever attempt to board your pet or attend a function for pets (like a pet fun day at a local park), since boarding kennels and any functions where groups of pets gather require proof of current rabies vaccination in order to gain entrance. It's worth it to forego these types of things, however, to keep the pet healthy.
I'm so glad to hear that they were able to save your little one's life. What a scary thing to have happen!
Ghilly
My dog also had a reaction to the rabies vaccine the last time she had it. She is due again this year but I will be seeing a holistic vet from now on. It is recommended highly!! In the meantime I have done tons of research on this topic and many others as well. Here are a couple of websites you may want to look through. They can help you understand what happened to your dog. I hope everything is okay now. It's scary, I know. :( Good luck.
http://vaccines.dogsadversereactions.com/
www.tendlife.com/general/talk-0911.html
http://www.thepetcenter.com/exa/vacreact.html
www.dogsadversereactions.com/vaccinePredisposed.html
www.dogs4dogs.com/JR_Articles/Rabies.html
That should give you plenty of info and may lead you to learning many other things about caring for your dog in a more healthy, holistic manor. I've learned a lot of things about these topics and all I can say is I have become very angry and distrustful. I have definitely taken on a more active approach towards my dogs' health. After all, she's my girl and I want her to be here as long as possible! :) Good luck and I hope I've helped somewhat!!