Beatrice did a disservice to the study, because she wrongly states it was seropositivity that matters—that is not true. The researchers did blood tests, which show if anyone ever had H. pylori at anytime in their lives (it’s an antibody test). However, the abstract clearly states they relied on fecal tests, which show CURRENT infection. So you had to have both to be “positive.”
So, this means if you need immunotherapy, you need to get rid of your H. pylori, first. That’s a pretty important thing to know.
If you had H. pylori in the past and eliminated it, you should likely be fine, according to this paper, it would seem.