If you remove what you consider vandalism, and the same editor puts it back, don’t automatically remove it again. Before reverting, you need to decide if this is a content dispute (Chapter 10) or just a persistent vandal. Here are the factors you should consider:
Is it clearly a case of vandalism? If, for example, the edit again replaced good content with a string of gibberish, then you don’t need to consider other factors—it’s vandalism. On the other hand, if the editor simply re-deleted a paragraph, perhaps it wasn’t.
Did the editor post anything about this matter on the article’s talk page? If so, except for cases of extremely obvious vandalism, treat the matter as a content dispute.
Did the other editor provide an edit summary when he reverted your edit, explaining his edit? If so, you should treat the matter it as a content dispute, not a matter of vandalism, assuming that all the other factors don’t point to vandalism. But if the editor failed to provide an edit summary (other than what Wikipedia added, such as section title), lean in the direction of repeated vandalism.
What’s the editor’s history – other vandalism or constructive edits? As discussed in this chapter, the editor’s user talk page (including its history), block log, and User contributions page provide you with a wealth of information about the editor. If they indicate that the user has at least some positive contributions and hasn’t been recently blocked, treat the matter as a content dispute.
What if you revert an edit the second time, and the same editor (or another IP address that it appears the same editor has migrated to—say, an IP address that previously had no edits whatsoever) does the edit (or a very similar one) for a third time? Then you want to read Wikipedia:Three-revert rule (shortcut: WP:3RR) very carefully. If you’re absolutely sure that any reasonable editor would agree that you’re fighting vandalism, go ahead and revert again. But if there’s any doubt at all, go to Chapter 10.