Evidence explainerVaginal Health: BV & Yeast

Bacterial Vaginosis That Keeps Coming Back: What the Trials Show

More than half of women had bacterial vaginosis again within a year of standard treatment in one cohort. A 2025 trial found that also treating male partners cut recurrence, though a 2026 meta-analysis says the question is not settled.

By Kymata Health editorial teamPublished October 10, 2026Last verified October 10, 2026

Medical review pending. Written by our editorial team from the studies and documents cited below; a credentialed clinician has not reviewed it yet. Educational only, not medical advice.

Key takeaways

  • BV recurred within 12 months in 58% of women followed after oral metronidazole; a past history of BV and a regular sex partner were linked to recurrence [1].
  • In the 2025 StepUp trial (164 couples assigned, stopped early for benefit), recurrence at 12 weeks was 35% when the male partner was also treated vs 63% with treatment of the woman only [2].
  • Partners took metronidazole tablets plus 2% clindamycin cream on the penile skin, twice daily for 7 days; side effects in men included nausea, headache and metallic taste [2].
  • A 2026 meta-analysis of 6 trials found no overall benefit from partner treatment; StepUp, the only trial with combined oral and topical therapy, was the exception [4].

How often BV comes back

In a cohort study of women treated with oral metronidazole (139 enrolled), 68 of the women followed (58%) had BV again within 12 months and 69% had abnormal vaginal flora [1]. A past history of BV, having a regular sex partner during the study and having female partners were linked to recurrence, while hormonal contraception was linked to less [1].

The authors concluded that recommended treatment was not preventing recurrence in most women and that the risk factors pointed to a possible role for sexual transmission [1].

The 2025 partner-treatment trial

StepUp randomized 164 couples in which the woman had BV and a monogamous male partner. In the partner-treatment group, the man took metronidazole 400 mg tablets and applied 2% clindamycin cream to the penile skin, both twice daily for 7 days; in the control group only the woman was treated [2].

The data and safety monitoring board stopped the trial after 150 couples had completed follow-up because treating the woman alone was inferior. In the modified intention-to-treat analysis of 137 women, recurrence within 12 weeks was 35% (24 of 69) with partner treatment vs 63% (43 of 68) without [2]. The open-label trial included only couples in a monogamous relationship [2]. The CDC's 2021 guidelines, written before it, do not recommend routine partner treatment, citing earlier trials; a phase 3 trial of oral metronidazole alone for male partners did not reduce recurrence [3].

Why the question is not settled

A 2026 meta-analysis pooled 6 trials with 953 couples and found no overall reduction in recurrence with partner treatment (risk ratio 0.97) [4]. Removing StepUp, the only trial that added topical therapy for the man, left a neutral result, so the authors said combined oral and topical treatment deserves more study [4].

Ask your clinician whether partner treatment fits your situation; StepUp included only women with a monogamous male partner [2].

Options for frequent recurrences

For women with multiple recurrences, the CDC says twice-weekly metronidazole gel for more than 3 months can reduce recurrences, though the benefit fades after stopping [3]. Limited data support a sequence of oral nitroimidazole, 21 days of vaginal boric acid and suppressive metronidazole gel [3].

The CDC also notes that high-dose vitamin D has not been shown to prevent BV recurrence and is not recommended [3]. For probiotics, see our vaginal probiotics guide.

Quick answers

Is BV a sexually transmitted infection?

The cause is not fully understood. BV is linked to new and multiple partners and is rare in women who have never been sexually active, but whether it comes from a single sexually transmitted pathogen is unknown [3].

Can I drink alcohol while taking metronidazole?

The CDC's 2021 guidelines say refraining from alcohol is unnecessary, because no convincing evidence supports a disulfiram-like reaction [3].

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References

  1. [1]High recurrence rates of bacterial vaginosis over the course of 12 months after oral metronidazole therapy and factors associated with recurrence. J Infect Dis, 2006. PMID 16652274
  2. [2]Male-Partner Treatment to Prevent Recurrence of Bacterial Vaginosis. N Engl J Med, 2025. PMID 40043236
  3. [3]Bacterial Vaginosis: Sexually Transmitted Infections Treatment Guidelines, 2021. Centers for Disease Control and Prevention, 2021.
  4. [4]The efficacy of male partner treatment to prevent recurrence of bacterial Vaginosis: A systematic review with Meta-Analysis of randomized controlled trials. Eur J Obstet Gynecol Reprod Biol, 2026. PMID 41780137

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