Asymptomatic Bacterial Vaginosis(aBV)increases the risk of acquiring multiple sexually transmitted diseases, HPV, gynecologic complications and adverse reproductive outcomes, and is speculated to affect 10 ~ 35% of women. Without intervention, a significant proportion of aBV would progress. Metronidazole is the most widely used treatment for aBV, yet the main challenge has always been the high rate of recurrence. Probiotics may increase the cure rate and reduce the recurrence rate of symptomatic bacterial vaginosis (sBV), while no study has compared the efficacy of probiotics and metronidazole on treating aBV. This study aims to fill the gap in understanding the difference in efficacy of probiotics and metronidazole in treating aBV by a multicenter, randomized, controlled trial. Participants received either a 10-day intravaginal probiotic capsules or a 7-day oral metronidazole. Follow-up were performed at the end of the 1st, 2nd, and 4th week after completing therapy. Women cured by either method were followed up with three additional visits. The primary outcome was the difference of cure rates between the two groups. The secondary outcome was to evaluate the recurrence rates among patients who were successfully cured using either method. 358 participants received probiotics and another 358 participants received metronidazole. The cumulative cure rates at the end of the 1st, 2nd, and 4th week were higher in probiotics group compared to metronidazole group (OR 1.063, P = 0.715; OR 1.324, P = 0.083; OR 1.338, P = 0.071), while the differences were not statistically significant. Women cured (144 in probiotics and 123 in metronidazole) were followed up. The difference of cumulative recurrence rates between the two groups were statistically significant at the end of the 2nd, 3rd, and 4th month (OR 0.212, P = 0.000; OR 0.160, P = 0.000; OR 0.119, P = 0.000). Adverse events were similar in the two groups (8.3%, 9.6% OR 0.858; P = 0.584). No life-threatening or severe adverse events were reported. Probiotics emerge as a superior therapeutic option for aBV due to their comparable cure rates, lower recurrence rates, and minimal side effects. Chinese Clinical Trial Registry (ChiCTR1800019436, 11/11/2018 ).
