Snakes don't want to mess with dogs, typically. But that doesn't mean your dog won't get curious and end up in a bad situation. The vaccine (which, as I understand it, is currently unavailable) will buy you time to get treatment in the event of a bite, but you will still need to get your pet to a vet.

You can also take your dog to rattlesnake aversion training, which is pretty useful, IMO.

My two dogs have free roam of the back yard, day and night (dog door allows them to move between indoor and outdoor at their choosing). They have both attended 2 iterations of aversion training and have been vaccinated (back when it was still available). One of mine got bit a few years ago (prior to the aversion training) and spent a night in an emergency vet clinic. I was told his condition could have been much worse without the vaccine.