Vaginal microbiota transplantation: what it is and what the studies say

Vaginal microbiota transplantation (VMT) consists of transferring the vaginal secretions of a healthy donor, rich in lactobacilli, into the vagina of a woman whose microbiota is altered. The aim is to rebuild the balance of "good" bacteria when the usual treatments are not enough. It is a promising idea, but today it remains an experimental treatment: for the time being it is carried out only within clinical trials, with donors who are selected and checked very carefully.

What the vaginal microbiota is

A community of microorganisms lives in the vagina: the vaginal microbiota. In healthy conditions it is dominated by lactobacilli, bacteria that produce lactic acid and keep the environment acidic, hostile to the germs that cause infections. When lactobacilli decrease and other bacteria, such as Gardnerella, take over, this is called vaginal dysbiosis. Its best-known form is bacterial vaginosis, which causes discharge and a bad smell but in many women causes no symptoms at all.

Vaginal dysbiosis is not just a nuisance: studies associate it with a higher risk of sexually transmitted infections, of preterm birth and of pregnancy loss, meaning miscarriage.

Why vaginal microbiota transplantation came about

Bacterial vaginosis is treated with antibiotics, such as metronidazole or clindamycin. They work well in the short term, but the condition often comes back: according to the studies cited by the Danish researchers, recurrences reach up to 60% within one year. Antibiotics reduce the "bad" bacteria, but lactobacilli do not always return to dominate; probiotics too, in most cases, change the microbiota only for a short time. For women who have continuous episodes, also described in our article on recurrent vaginitis, the options are few.

The idea of the transplant comes from the gut. Fecal microbiota transplantation, that is, the transfer of stool from a healthy donor, has proved very effective against recurrent Clostridioides difficile infections. The reasoning is the same: instead of adding one or two strains of bacteria, as a probiotic does, an entire ecosystem that is already balanced is transferred.

How vaginal microbiota transplantation is performed

In the published studies the procedure follows a few common steps:

1. Donor selection: a healthy woman of childbearing age, with a microbiota dominated by lactobacilli, who undergoes a long list of tests.
2. Collection of the material: the donor collects her vaginal secretions, which the laboratory checks sample by sample and can store frozen. In a US study the lactobacilli remained viable for more than six months at −80 °C.
3. Preparation of the recipient: in some studies the recipient first takes a course of an antibiotic or an antiseptic, to reduce the bacteria present in the vagina, which are in the wrong proportions and responsible for the dysbiosis; in others the transplant is done without any specific preparation of the recipient.
4. Transplant: the material is introduced into the vagina, sometimes in several sessions, in different menstrual cycles.

What the studies on vaginal microbiota transplantation really say

Studies in humans are still few, each with few patients. A review of the literature updated to October 2023 counted three, with a total of 36 women, plus five registered studies under way. To understand what we know, case series must be separated from randomized trials.

Case series: encouraging results

• The first study (Israel, 2019). Five women with symptomatic bacterial vaginosis that was recurrent and resistant to treatment, treated first with an antibiotic (clindamycin or metronidazole) and then with the transplant. In four out of five the symptoms disappeared and the microbiota returned to being dominated by lactobacilli, with a remission that lasted throughout follow-up, from 5 to 21 months. In three women, however, the transplant was repeated, and one had to change donor. There were no side effects.
• A single case (Denmark, 2023). A 30-year-old woman with severe dysbiosis and a history of two stillbirths and one late miscarriage received a single transplant, without antibiotics. Her microbiota became dominated by the donor's lactobacilli, as confirmed by genetic analysis, and remained stable for a year and a half. Five months later the woman became pregnant and gave birth at term. It is an important result, but it concerns a single patient.
• A US pilot study (2025, not yet published in a journal). Eight women with recurrent vaginosis, after an antibiotic, received either the transplant from a single donor or a placebo. In three of the four treated women the microbiota became dominated by Lactobacillus crispatus after one month, and in two the result lasted at least six months; none of the women given placebo had the same change. It is a preprint: the data have not yet been checked by other experts.

The first randomized trial: negative main result

The first randomized, placebo-controlled trial, carried out at Copenhagen University Hospital between 2021 and 2023 and published in The Lancet Microbe in 2026, involved 49 women aged 18 to 40 with vaginal dysbiosis, with or without symptoms. 37 received the transplant and 12 a placebo, up to three times over three menstrual cycles, without antibiotics beforehand. Neither the women nor the researchers knew who was receiving what.

The main result was negative: the dysbiosis resolved with the same frequency in the two groups, with no significant difference. In a later phase of the trial, ten women who had not responded received an antiseptic treatment before a new transplant, and in five of them the microbiota changed. The researchers conclude that the transplant without preparation did not work better than placebo, and that preparation with an antiseptic might improve its effectiveness: this needs to be verified in new studies.

Pregnancy and fertility

Interest in the transplant also concerns fertility and pregnancy, because dysbiosis is associated with pregnancy loss and preterm birth. Today, however, the only data in this field is the single Danish case; the randomized trial excluded pregnant women. There is no evidence that the transplant improves fertility or reduces pregnancy loss, and it should not be considered a treatment for female infertility.

Vaginal microbiota transplantation should not be confused with so-called "vaginal seeding", that is, the transfer of the mother's vaginal secretions to a newborn delivered by cesarean section: it is a different practice, investigated in other clinical trials.

Safety: how donors for vaginal microbiota transplantation are chosen and checked

The main risk of the transplant is passing an infection from the donor to the recipient. For this reason the studies use very strict selection protocols, which in the United States have been approved by the FDA. Donors:

• are healthy women, with a microbiota dominated by lactobacilli, with no history of vaginosis and no recent genital infections;
• have blood tests and swabs for HIV, hepatitis A, B and C, syphilis, genital herpes and other viruses such as cytomegalovirus, as well as gonorrhea, chlamydia, trichomonas and Mycoplasma genitalium;
• have a normal Pap test and a negative test for the high-risk types of human papillomavirus (HPV), the virus responsible for genital warts and cervical cancer;
• repeat the tests before, at the end of and about one month after the donation period, so as not to risk missing newly acquired infections, which tests do not detect right away;
• do not have sexual intercourse and do not use vaginal products during the donation period.

Every single sample is also checked in the laboratory, for example for HPV and for the absence of seminal fluid.

In the published studies the transplant was well tolerated: in the Copenhagen trial adverse effects were just as frequent with the transplant as with placebo (42% in both groups), none of them serious; during the trial one woman acquired a new HPV infection, which the researchers considered unrelated to the treatment. The numbers, however, are too small to rule out rare or long-term risks.

Beware of "do it yourself"

Vaginal microbiota transplantation must never be done at home, for example using the secretions of a friend or a partner. Without the tests described above there is no way of knowing whether the material transmits HIV, hepatitis, HPV, herpes, syphilis or other infections, which sometimes cause no symptoms and are not visible. Even a donor who feels well may have an ongoing infection or a dysbiosis without knowing it, and pass it on. No one checks the collection, storage and amount of material. The risk of doing serious harm is real, while the benefit has not been proven even in controlled trials.

Anyone who has vaginosis or vaginitis that keeps coming back should talk to their gynecologist, who can assess the available treatments and point out any clinical trials to take part in.

Where is vaginal microbiota transplantation done today?

Vaginal microbiota transplantation is done only within clinical trials. In the United States, for example, it is regulated as an investigational drug and requires a specific authorization from the FDA. On the international registry ClinicalTrials.gov, consulted on 22 October 2026, six studies are listed:

• Israel (Hadassah, Jerusalem): a phase 1-2 study on recurrent vaginosis, active but no longer open to new patients, and one, open, on the genital microbiota of the male partners of the treated women;
• United States (Boston): a phase 1-2 study, open;
• Denmark (Copenhagen): the randomized trial described above, completed;
• Ireland (Cork): a study on vaginal dysbiosis sponsored by a company, completed;
• United States (Johns Hopkins): a study withdrawn before it started.

In the United States the only study open to new patients on ClinicalTrials.gov is the one in Boston; in the United Kingdom no study of vaginal microbiota transplantation is listed, either on ClinicalTrials.gov or on the UK's ISRCTN registry (both consulted on 22 October 2026). Anyone who comes across offers of this treatment outside a registered study should be wary of them.

Frequently asked questions

Does vaginal microbiota transplantation cure bacterial vaginosis?

We do not know yet. In the small case series many women improved, but in the first randomized trial the transplant without antibiotics did not work better than placebo. Larger studies are needed.

Is it the same as vaginal probiotics?

No. A probiotic contains one or a few strains of bacteria produced in a laboratory; the transplant transfers the entire community of microorganisms of a donor. This is exactly why it is more promising, but also more delicate from a safety point of view.

Can I do it with the secretions of someone I trust?

It is not safe. Without thorough and repeated laboratory tests, the risk of transmitting infections, even serious ones, is real.

Do you need to take antibiotics first?

In the studies in which it worked best, the transplant was preceded by an antibiotic or an antiseptic. This is one of the questions that the next studies will have to answer.

Does it also work against candida?

Studies in humans concern bacterial vaginosis and dysbiosis, not candida.

Does it help you get pregnant?

There is no evidence. There is only one described case of pregnancy after the transplant, and it is not enough to draw conclusions.

References

1. Lev-Sagie A, Goldman-Wohl D, Cohen Y, Dori-Bachash M, Leshem A, Mor U, et al. Vaginal microbiome transplantation in women with intractable bacterial vaginosis. Nature Medicine. 2019. PubMed
2. Wrønding T, Vomstein K, Bosma EF, Mortensen B, Westh H, Heintz JE, et al. Antibiotic-free vaginal microbiota transplant with donor engraftment, dysbiosis resolution and live birth after recurrent pregnancy loss: a proof of concept case study. eClinicalMedicine. 2023. PubMed
3. Wrønding T, Vomstein K, Lundgaard AT, DeLong K, Mollerup S, Mortensen B, et al. Vaginal microbiota transplantation for treatment of vaginal dysbiosis without the use of antibiotics: a double-blind, randomised controlled trial in women with vaginal dysbiosis. The Lancet Microbe. 2026. PubMed
4. Hussain FA, Bergerat A, Kelly J, Demidkina BC, Worrall D, Xu J, et al. Donation strain engraftment demonstrates feasibility of vaginal microbiota transplantation to prevent recurrent bacterial vaginosis. medRxiv (preprint, not peer reviewed). 2025. PubMed
5. Yockey LJ, Hussain FA, Bergerat A, Reissis A, Worrall D, Xu J, et al. Screening and characterization of vaginal fluid donations for vaginal microbiota transplantation. Scientific Reports. 2022. PubMed
6. DeLong K, Bensouda S, Zulfiqar F, Zierden HC, Hoang TM, Abraham AG, et al. Conceptual Design of a Universal Donor Screening Approach for Vaginal Microbiota Transplant. Frontiers in Cellular and Infection Microbiology. 2019. PubMed
7. Luo H, Zhou C, Zhou L, He Y, Xie RH. The effectiveness of vaginal microbiota transplantation for vaginal dysbiosis and bacterial vaginosis: a scoping review. Archives of Gynecology and Obstetrics. 2024. PubMed
8. ClinicalTrials.gov, search "vaginal microbiota transplant" (NCT02236429, NCT04855006, NCT04517487, NCT04046900, NCT05963711, NCT05850078, NCT03769688), also filtered by location United States and United Kingdom, consulted on 22/10/2026. ClinicalTrials.gov. ISRCTN registry, search "vaginal microbiota" (22 results, none on vaginal microbiota transplantation), consulted on 22/10/2026. ISRCTN