Bacterial Vaginosis, Affecting 1 in 3 Women, May Be an STI

New Australian research challenges decades of BV treatment protocol.

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Bacterial vaginosis (BV), affecting more than 3 million women in the United States each year, is in fact a sexually transmitted infection (STI), according to a new study from Australia.

Published in The New England Journal of Medicine on March 5, the research shows that treating both sexual partners at the same time—rather than just the woman—cuts reinfection rates by about half.

The new understanding, built on decades of research, represents a major shift in how we approach BV and its treatment, offering new possibilities for women affected by its recurrent symptoms, such as discharge, itching, and inflammation, as well as serious risks such as infertility, premature birth, and newborn deaths.

“We’ve proven that reinfection [from partners] is driving a significant portion of recurrence—in fact, the majority,” Catriona Bradshaw, a clinician-researcher who co-led the study, told The Epoch Times.

BV has long been linked to a disrupted vaginal microbiome. Globally, it affects one in three women.

In a healthy vagina, Lactobacillus bacteria protect against infections and support healthy pregnancies. However, in BV, these beneficial bacteria are replaced by a mix of harmful microbes, including Gardnerella, Atopbium, and Mobiluncus bacteria.

Treating BV as a simple vaginal imbalance, meaning that only the female is treated with antibiotics, rather than as an STI, for which both partners receive treatment, may be why more than half of women experience recurrence within three months, Lenka Vodstrcil, co-lead researcher, told The Epoch Times.

If a person continues to have sex with the infected partner, she will very likely get reinfected, she said.

Partner Treatment

In the randomized controlled trial involving 164 monogamous, heterosexual couples, researchers found that treating both partners almost halved BV recurrence, offering a “very simple, effective strategy” to address a long-standing problem, according to Bradshaw.

Women whose partners also received the one-week treatment of the oral antibiotic metronidazole with the addition of topical clindamycin cream for men to apply their genital areas had a recurrence rate of only 35 percent, compared to 63 percent in the control group, which included only the women being treated for the infection.

All participants were selected for having a high burden of risk factors for BV recurrence. Eighty-seven percent of women had a history of recurring BV, and 80 percent of men were uncircumcised—known to increase the risk of BV transmission due to potential bacterial buildup.

Additionally, one-third of the women used intrauterine device (IUD) birth control, which can provide a surface for bacteria to adhere to, making infections more persistent and harder to treat, the researchers noted.

Not all participants who were treated were cured. IUD users, particularly those with copper IUDs, had higher rates of persistence, meaning they were not cleared of the infection after treatment. IUD users are also linked to higher rates of BV recurrence.

Reframing the Evidence

For more than 15 years, Vodstrcil and Bradshaw have investigated the causes of BV, with their research providing compelling evidence for its classification as an STI, supported by both epidemiological studies and molecular research.

Their previous research shows that BV is rare in women who have never had sex, and recurrence is often linked to ongoing sexual partnerships. Epidemiological evidence suggests that a first-time BV infection is often linked to having a new sexual partner, said Vodstrcil, who is also the deputy head of the Genital Microbiota and Mycoplasma Group at the Melbourne Sexual Health Centre.

Advances in molecular technology have further supported this theory, revealing that the bacteria responsible for BV are also present on penile skin and in the urethra of men.

Bradshaw notes that many clinicians have long suspected that BV is an STI, given its association with sexual activity, such as changing partners and inconsistent condom use. BV often develops within days to weeks after sexual contact, making it similar to other STIs in terms of its timing after exposure.

“I would see women who would say, ‘I used to have it all the time, and then I broke up with my boyfriend and didn’t have BV, we’re back together, and I’ve got it straight back again,’” Bradshaw said.

Rethinking Old Studies

Earlier studies, however, questioned this theory. One involved teenage girls, some of whom were virginal, in whom BV was found in a few cases. This led to the assumption that BV wasn’t sexually transmitted.

Bradshaw suggests that the conclusions of these studies may be affected by potential biases, particularly in face-to-face interviews with 16-year-old girls. She raises the possibility that the gender of the interviewers, often male gynecologists, could have influenced the girls’ willingness to disclose sexual activity.

Bradshaw designed a study using anonymous questionnaires and self-collected samples from university students. The results revealed a clear pattern: Women with no sexual activity had no BV; those with non-penetrative sexual activities had a small amount; and women who had engaged in penetrative sex had significantly higher rates of BV.

Previous research involving treatment of male partners did not show improved cure rates for women. However, Bradshaw said that the study had design limitations, including not using a combination of oral and topical antibiotics to fully clear BV bacteria in men, especially from the skin of their genitals.

Vodstrcil’s analysis from their newest research found that when men didn’t fully adhere to their treatment, women’s recurrence rates were higher.  The women’s BV was least likely to come back when the men followed the treatment—both pills and cream—as instructed.

The Challenge of Treatment

BV remains challenging because scientists haven’t pinpointed a single cause. A mix of harmful bacteria thrives when the vaginal microbiome is disrupted, often forming a biofilm—a protective matrix that shields the bacteria from treatment. Also, even after treatment, the microbiome may not fully recover, leaving the vagina vulnerable to reinfection. Some women, such as those with copper IUDs, may be less responsive to treatment.

While adjunct therapies such as probiotics may support the gut microbiome, there’s limited evidence that they benefit the vaginal microbiome. However, a specific probiotic called LACTIN-V, a vaginal lactobacillus species, has shown promise.

A 2020 study of 228 women, published in the New England Journal of Medicine, found that African women who used LACTIN-V for 12 weeks, alongside one week of oral metronidazole antibiotics, experienced a modest 30 percent reduction in BV recurrence.

In most cases, however, reinfection is primarily driven by the presence of an infected partner, according to Vodstrcil and Bradshaw.

“The external partner is still there, and sexual activity can disrupt the balance,” Vodstrcil said.

This shift in understanding could lead to updates in global health guidelines, including recommendations for condom use to help prevent both getting BV and having it recur, Vlodstrcil said.

The researchers have launched a new website to help clinicians and couples implement the partner-treatment strategy worldwide.

The website features links to the study and participants’ experiences. It also includes information about side effects, such as nausea, headaches, and a metallic taste—common when taking antibiotics.

Additionally, the site provides simple labeling instructions for pharmacists, who will need to repackage the clindamycin cream as a product men can also use.