The first one isn't a valid construction. You don't want to combine a causative structure with a reflexive pronoun after the main verb. The second one works because the reflexive pronoun "ourselves" is modifying the helping verb "get". It's not necessary to include the reflexive pronoun, but it's certainly not an error to so despite what another poster says below. In grammatical terms, it's called a causative structure when you say "get something done" or "have something done": and there's nothing wrong with combining it with a reflexive pronoun that follows the helping verb like in your second example. See unit 46 of the textbook English Grammar in Use to learn more about causative structures with "get" or "have."

#1 is poor style. It would make more sense if you wrote it as: "We ourselves got vaccinated" in which "ourselves" is an unnecessary word that serves only to emphasizes "we". It is better to omit "ourselves": "We got vaccinated against hepatitis." The meaning of #2 is more clear but the word "ourselves" is still superfluous. The over-used verb "get" should be used as little as possible. It means a thousand different things and pushes honest words out of sentences. Use a more direct verb: "We had ourselves vaccinated against hepatitis." Your vocabulary will improve if you avoid saying "get". It is a temptation to use it because it makes it easy to speak English. It makes it unnecessary to learn the verbs. Although it is a convenience, it cheapens your spoken language. I recommend using it only in common idiomatic expressions, like "they get along well" "it's time to get going"

I think in the first sentence, the action of getting vaccinated is actually willingly taken by the subjects. In the second one, it sounds more like an obligation. But I’m not very much sure of that, tbh! 😅😂