Vaginal microbiota transplantation for treatment of vaginal dysbiosis without the use of antibiotics: a double-blind, randomised controlled trial in women with vaginal dysbiosis

BACKGROUND: A vaginal microbiota dominated by Lactobacillus species is associated with reduced risk of infection and adverse reproductive outcomes. Effective interventions to restore healthy microbiota remain scarce. In this study, we aimed to assess the efficacy of vaginal microbiota transplants (VMTs) without antibiotic pretreatment in achieving conversion to a Lactobacillus-dominated vaginal microbiome.

METHODS: This single-centre, double-blind, randomised controlled trial was done at Copenhagen University Hospital (Hvidovre, Denmark) between June 1, 2021, and March 1, 2023. We enrolled women aged 18-40 years with asymptomatic or symptomatic molecular vaginal dysbiosis (<10% total relative abundance of Lactobacillus spp and >20% relative abundance of Gardnerella spp, Fannyhessea vaginae, and Prevotella spp) who were otherwise healthy premenopausal women and not pregnant as recipients; donors were healthy women aged 18-40 years with a Lactobacillus-dominated vaginal microbiota (>80%) and a low (<5%) abundance of Gardnerella spp, F vaginae, and Prevotella spp, and negative screening for sexually transmitted infections. Participants were randomly assigned (3:1) to the intervention or placebo through a computer-generated schedule with block randomisation and stratification by hormonal contraception. Participants and investigators were masked to the group. Up to three administrations of VMT or placebo were given across three menstrual cycles, with follow-up for six cycles. The primary endpoint was resolution of dysbiosis at any timepoint during follow-up, defined as at least 70% relative abundance of Lactobacillus spp and less than 10% combined abundance of Gardnerella spp, F vaginae, and Prevotella spp, as assessed by shotgun metagenomic sequencing of vaginal samples. This analysis was done in the intention-to-treat population, excluding any participants who withdrew consent. An extension study assessed the effect of antiseptic pretreatment before additional VMT in refractory participants. This study was registered with ClinicalTrials.gov (NCT04855006) and is completed.

FINDINGS: A total of 302 women were screened, of whom 49 were enrolled. 37 women were randomly assigned to the VMT group (mean age 26·1 years [SD 3·8]) and 12 to the placebo group (27·3 years [4·8]). The primary outcome showed no significant difference in dysbiosis resolution between active and placebo groups (HR 0·65; 95% CI 0·20-2·16, p=0·49). In an extension study of refractory participants, five (50%) of the ten women who received antiseptic pretreatment followed by VMT had a microbiome conversion. Adverse events occurred in 15 (42%) VMT participants and five (42%) placebo participants; none were serious or led to withdrawal. A single pregnancy and one new human papillomavirus infection occurred, both unrelated to treatment.

INTERPRETATION: VMT without antibiotics did not significantly improve microbiome conversion in this trial. However, findings from the extension study suggest that antiseptic pretreatment might enhance efficacy. Future trials should explore optimised dosing and use donor engraftment as a primary outcome.

FUNDING: Freya Biosciences.