240 participants with Long COVID will be randomly assigned to either a probiotic or placebo group in a 1:1 ratio for twelve weeks. Participants will track symptoms using an app for three weeks before the study, and for the last three weeks of the treatment. Participants will answer online questionnaires about their symptoms at 0, 4, 8, and 12 weeks. A subgroup of 60 participants will attend the laboratory for blood tests, cognitive function tests and gut microbiome analysis at 0 and 12 weeks. This group will also wear activity trackers for two weeks before the study, and for the final two weeks of the study.
