BACKGROUND: Bacterial vaginosis affects 15 to 50% of women of reproductive age, 
and recurrence is common after treatment with an antibiotic agent. The high 
incidence of recurrence suggests the need for new treatments to prevent 
recurrent bacterial vaginosis.
METHODS: We conducted a randomized, double-blind, placebo-controlled, phase 2b 
trial to evaluate the ability of Lactobacillus crispatus CTV-05 (Lactin-V) to 
prevent the recurrence of bacterial vaginosis. Women 18 to 45 years of age who 
had received a diagnosis of bacterial vaginosis and who had completed a course 
of vaginal metronidazole gel as part of the eligibility requirements were 
randomly assigned, in a 2:1 ratio, to receive vaginally administered Lactin-V or 
placebo for 11 weeks; follow-up occurred through week 24. The primary outcome 
was the percentage of women who had a recurrence of bacterial vaginosis by week 
12.
RESULTS: A total of 228 women underwent randomization: 152 to the Lactin-V group 
and 76 to the placebo group; of these participants, 88% in the Lactin-V group 
and 84% in the placebo group could be evaluated for the primary outcome. In the 
intention-to-treat population, recurrence of bacterial vaginosis by week 12 
occurred in 46 participants (30%) in the Lactin-V group and in 34 participants 
(45%) in the placebo group (risk ratio after multiple imputation for missing 
responses, 0.66; 95% confidence interval [CI], 0.44 to 0.87; P = 0.01). The risk 
ratio for recurrence by week 24 (also calculated with multiple imputation for 
missing responses) was 0.73 (95% CI, 0.54 to 0.92). At the 12-week visit, L. 
crispatus CTV-05 was detected in 79% of participants in the Lactin-V group. The 
percentage of participants who had at least one adverse event related to 
Lactin-V or placebo by week 24 did not differ significantly between the groups. 
The percentage of participants with local or systemic adverse events was similar 
in the two groups.
CONCLUSIONS: The use of Lactin-V after treatment with vaginal metronidazole 
resulted in a significantly lower incidence of recurrence of bacterial vaginosis 
than placebo at 12 weeks. (Funded by the National Institutes of Health; 
ClinicalTrials.gov number, NCT02766023.).