At this time, there is no rabies vaccine approved for captive bred wolves and wolfdogs. This leaves wolfdog owners in the uncomfortable position of either denying that their animal is part wolf, in order to keep their animal safely & legally vaccinated...or not vaccinating the animal at all.
Why, you ask, does the IMRAB vaccine--labelled for use in dogs, cats, sheep, cattle, horses, and ferrets--supposedly not work on dogs mixed with nondomesticated dog (i.e, "wolf")?  Especially in light of the fact that the testing was done on beagles, then extrapolated out to include all other breeds of dog...including German Shepherd dogs, which were verifiably crossed back to wolf only a century ago, and all the "breeds" of wolfdog such as the Saarloos and Czechoslovakian Wolfdog? Also in light of the fact that wolves, coyotes, and foxes in the wild and in zoo settings ARE vaccinated for rabies by means of bait drops?

The issue is a political one, not a scientific one, sad to say. None of the vaccine companies feel that any financial gain from approving the vaccine for wolfdogs is worth the political flak that comes with "endorsing wolf crosses as acceptable for private ownership". I decided to call all the major vaccine manufacturers at one point, and discuss the issue with them, in hopes that they could help wolfdog owners find a way to get this crucial vaccine approved for their animals. (The reason approval is so important to us as a group, is because the lack of a legal vaccine is a common excuse used by lawmakers ignorant of true wolfdog temperament, when trying to promote breed-specific legislation against them. Wolfdogs are already illegal in many places...if they are ever to gain the acceptance that other--more dangerous, I might add!--breeds of dog enjoy, the rabies approval MUST be obtained.)

I started with Rhone-Merieux (which has now incorporated Solvay): manufacturer of IMRAB, the most commonly used rabies vaccine. The lady I spoke with at length from Merieux was very nice, and actually seemed interested in looking into this for me...she talked to a bunch of people there, including the head of the research/testing department...but his final word is that he is not interested in working with us on this. In a nutshell--Merieux wants no part of it because (and she actually told me this directly): "We already know the vaccine works. Why bother with a formal study? Use it...but you will be using it off-label, because we want no involvement with the bad press associated with condoning wolf hybrids." They do use this vaccine for zoo animals and bait drops.
But...Merieux is not the only fish in the sea.

Pfizer Pharmaceuticals in Groton, CT (Technical Services, Animal Division: 800-366-5288 ) makes the Defensor vaccine, for use in dogs, cats, sheep, & cattle. They are also concerned with bad press by association with us, as they'd recently had an "incident" whereby they were involved with vaccinating the animals of a puppymiller...and they took alot of heat for "promoting puppymills". However, they aren't dead-set against it, either. The girl I spoke with (though she *was* the technical advisor on duty) knew very little about the specifics of initiating a formal study...other than that THEY would need to do the study themselves and that a request would need to be sent to someone higher up than she, in the Clinical Testing Division. Got the snailmail addy from headquarters, it is:

Pfizer Animal Health
812 Springdale Dr
Exton, PA 19341
ATTN: Clinical Trials
Perhaps, if a proposal for a study can be written up, this would be a viable place to send it.

Schering-Plough Animal Health distributes Pfizer's other rabies vaccine, RABDOMUN (on-label: dogs, cats, sheep, cattle), and is, itself, a biochemical/pharmaceutical company...however, they do not produce their own rabies vaccine. They buy through Pfizer only.

Fort Dodge in Overland Park, KS, manufactures RABVAC (Dog, cat, horse). Their Technical Services division is not equipped to handle such inquiries (as she put it, "We just don't get calls like this." ;) BUT, she gave me both a fax number: (913) 664-7220 and a snailmail addy:

Fort Dodge Animal Health
ATTN: Professional Services
PO BOX 25945
Overland Park, KS 66225-5945
To which an inquiry could be made. (i.e. to ask them "what it would take", to get Ft Dodge to initiate formal testing) She added that it should include a phone number, as they are likely to call back to discuss it. Another viable (?) place to send a formal proposal, if we can get enough folks involved it make it fly.

Lastly: there is a smaller company--Intervet--in Delaware, who makes the PRORAB vaccine (internationally known as Nobivac) for dogs, cats, & sheep. Intervet's main number is (302) 934-8051; when talking to any of these folks, you want the Technical Services, Companion Animals division. I'd asked her if funding was the main obstacle in getting approval, and she agreed that it was probably the biggest one...but also noted that it would take years for a formal study to be completed. She took my name and number, and said she will discuss it with their staff veterinarians, was not very encouraging.

One of the wolfdog community's more recent attempts to gain approval was by making use of the American Society of Mammalogists' reclassification of the wolf and dog as the same species. In light of this decision, if the wolf and dog are the same species...and the rabies vaccine is approved BY SPECIES, then wolves and wolf/dog crosses are already included in any product labelled for use in DOGS (canis lupus). Formally, this update needed to be approved by the USDA, and a proposal was under consideration. Vaccination data was sent, scientific documentation proving the validity of the vaccine was sent, and the initial comments put out by USDA strongly suggested that approval was forthcoming. However, during the comment period, anti-companion animal extremists such as the Humane Society of the United States (HSUS) and People for the Ethical Treatment of Animals (PETA) <<<look
HERE if their true agenda is news to you!>>> put heavy pressure on USDA to deny the approval. In addition, the American Veterinary Medical Association (AVMA)--even though they are well aware of the effectiveness of the vaccine--decided that this should be an ethical issue rather than a scientific one, and allowing wolfdogs to be vaccinated "sends the message that they are acceptable companions". They advised USDA to deny the request as well. Unfortunately, the veterinarians' lobby carries a lot of weight...more than it truly should, in matters where their knowledge base is the same as that of the general public. Veterinarians are humans like the rest of us, and (unless they have experience with them) know no more of the details of various dog breeds than the average citizen...and are therefore no more qualified than anyone else to make judgement upon them. Many, many wolfdog owners (including myself) have found veterinarians to be sorely lacking in any knowledge of this type of animal. Regardless, the end result is that politics prevailed, and approval was denied...leaving many good animals in jeopardy.

Looking forward, it seems that the best angles, from a going-through-the-manufacturers standpoint, would be to write to Pfizer and Fort Dodge...and try to convince them that there is not only enough interest to warrant doing the testing, but many people willing to put their money where their mouth is and contribute funds (and possibly animals?) to the research. All suggestions are worth considering at this point, so if you have ideas on the subject, by all means give them a try! Or, write to one of these excellent groups working towards rabies vaccine approval: 
RAFT and The Wolfdog Coalition.  Both these groups can give you much more detailed information on the history of the rabies controversy than I can, as they have been involved with it in depth for many years.
The Rabies Controversy