D.B.
Kids go through this all the time. It's frustrating but it's usually a phase. It's possible there's a connection with the immunizations or with a low grade touch of something (fever, earache) but honestly, you see stuff like this on Mamapedia all the time, so everyone's going through it. Most kids can't articulate their fears anyway (and certainly not in the middle of the night), and they don't remember their dreams.
The best thing to do is put him back in his bed, comfort him, let him know he's safe in his own wonderful room in his own wonderful house, pat his back, wish him sweet dreams, and go back to bed. Don't engage him in a whole lot of talk - he's not really awake, and he just needs reassurance. I think praying is fine, but sometimes we need to "pray with our feet" - meaning we have to take action to solve problems! You can try a night light or a dream catcher if that would help, but consistency and a completely relaxed attitude and tone from you will do a lot more. He'll come through this phase and be fine.