Trial provides ‘substantial evidence’ that bacterial vaginosis is sexually transmitted
Key takeaways:
- Bacterial vaginosis recurrence was nearly halved when male partners were also treated for the condition.
- Experts said the results “provide substantial evidence” that BV is sexually transmitted.
The addition of treatment for male partners reduced the recurrence of bacterial vaginosis among women enrolled in a randomized trial compared with treating only the women, researchers reported.
The trial of monogamous couples included a group in which male partners received oral and topical antimicrobials in addition to the female partner being treated for bacterial vaginosis (BV).
The findings showed clearly that BV — the most common vaginal condition among women aged 15 years to 44 years, according to the CDC — can be sexually transmitted, experts said.
According to the CDC, BV is a result of imbalanced “good” and “bad” bacteria in the vagina. Douching, not using condoms and having multiple sex partners can increase a person’s risk, the agency noted.
BV affects roughly 21 million women in the United States, with more than 58% experiencing recurrent infections, according to experts. It has been linked to persistent STIs, such as chlamydia.
Lenka A. Vodstrcil, PhD, a senior research fellow in the Melbourne Sexual Health Center at Monash University in Melbourne, Australia, and colleagues analyzed data on 164 couples as part of an open-label, randomized controlled trial in which a woman had BV and was in a monogamous relationship with a male partner, according to the study.
The researchers assigned 81 couples to a group in which the male partner was treated with 400 mg of metronidazole and a topical clindamycin cream. They assigned 83 couples to a control group in which only the woman was treated. Women in both groups received first-line treatment — 400 mg of metronidazole tablets twice daily for 7 days and either topical clindamycin cream or metronidazole gel. The researchers followed both groups for 12 weeks.
The trial was stopped after 150 of the couples had finished the 12-week follow-up period because “treatment of the woman only was inferior to treatment of both the woman and her male partner,” the researchers wrote.
According to the study, recurrence occurred in 24 of 69 (35%) women in the partner-treatment group (recurrence rate, 1.6 per person-year; 95% CI, 1.1-2.4), compared with 43 of 68 (63%) women in the control group (4.2 per person-years; 95% CI, 3.2-5.7).
In an editorial published with the study, Christina A. Muzny, MD, MSPH, professor of medicine at the University of Alabama-Birmingham, and Jack D. Sobel, MD, dean of the Wayne State University School of Medicine, wrote that despite data supporting sexual transmission of BV-associated bacteria, the condition is generally not treated as an STI.
As a result, they wrote, there have not been effective strategies to prevent transmission of BV-associated bacteria, aside from the use of condoms.
“The results of this trial are timely and important,” Muzny and Sobel wrote. “They provide substantial evidence supporting the role of sexual transmission of BV-associated bacteria, particularly within regular sexual partnerships.”
“They also signify a need for a major change to the treatment approach of women with BV with respect to how women should be counseled regarding the origin of their infection and to the need to engage their male partners in sharing responsibility for transmission and treatment,” they wrote.
References:
- CDC. Bacterial vaginosis (BV): About bacterial vaginosis (BV). https://www.cdc.gov/bacterial-vaginosis/about/index.html. Updated Dec. 11, 2023. Accessed March 5, 2025.
- Munzy CA and Sobel JD. N Engl J Med. 2025;10.1056/NEJMe2500373.
- Vostrcil LA, et al. N Engl J Med. 2025;10.1056/NEJMoa2405404.
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