If you do go the titer route, make sure your vet sends it directly to Kansas State University. They are the only lab that does both core vaccine titers (distemper/adenovirus/parvo) and rabies titer.
There are two rabies titers. You want the cheap one. The very very expensive one is only required for export purposes.

There is another holistic vet who advocates a method of 'natural immunization' that involves repeated exposures to high dog traffic areas for gradually increasing time periods ( starting with just setting pup down and gradually increasing times by 30 second intervals every few days up to an hour)
A few of my clients have done this and do get protective immunity per titer information but I have held too many dying puppies to advocate. I would still do the titer and see the puppy...I just wouldn't push that method.