I have to do some veterinary research.

I took the cats in for their yearly check up today.
They're both looking great at 14 years of age, although Ash does need a dental soon.

I had been expecting to get their three year rabies shots, but apparently they are no longer giving the three year shot and only offer the one year version.

Supposedly the three year version has some additive that irritates tissues and was causing vaccine sarcomas.
The vaccine that does not have the additive supposedly does not last longer than a year.

Now, I don't want to risk the sarcomas (hugs to Tango, who is fighting a similar problem),
but I also don't want to be constantly stressing out the immune systems of my two 14 year old cats.

(I'm sorry to say I've had some past bad experiences with vets that make me less than trusting.)

So the questions are:
Is the one year version really safer?
Is the three year version safe?
...and where the heck do I find this out?

*sigh*