My dog is lost, he is needing his yearly shots, are they effective for longer than a year?

My dog had gotten lost last month, it is now time for his shots, some neighbors have seen him, so we know he is around; but we are unable to get him home yet. We live in the south where there is a lot of wildlife and woods. My question is now that he is due for his shots how worried should I be that he will contract rabies or another viral ailment? Do the vaccines really wear out at exactly a year or is there a bit of window before his immunity is truly gone.