Evvy’s Research Shows BV Isn’t One Condition — It’s Many

Bacterial vaginosis (BV) is the most common vaginal infection in people with vaginas, and also one of the most frustrating. For decades, BV has been used as an umbrella term for an “overgrowth of bad bacteria,” even though that overgrowth can look very different from person to person. That’s part of why BV so often comes back after treatment, leaving many women (and doctors) wondering why it’s so hard to get rid of for good.

New research from Evvy shows that BV isn’t one biological condition, but a spectrum of different microbial states, even when symptoms look the same. This means people with the same diagnosis can have very different bacteria driving their symptoms, which helps explain why the same treatment can work for one person and barely help another.

Based on data from over 100,000 vaginal microbiome samples, this research offers a clearer picture of what’s really going on beneath the surface, and lays the groundwork for more precise, evidence-driven care.

Why BV is so hard to treat 

BV happens when the vaginal microbiome gets out of balance. In a healthy vagina, protective Lactobacillus bacteria help keep things stable and acidic. In BV, those protective bacteria drop, and other bacteria overgrow. While this general pattern has been understood for decades, the way BV is diagnosed hasn’t kept up with modern microbiome science.

BV is still diagnosed using tools that were created before we could see the vaginal microbiome in detail. Today, most providers rely on tools like Amsel’s criteria or the Nugent score. These methods are useful for identifying that BV is present, but they don’t show which specific bacteria are driving the imbalance or how different one person’s BV may be from another’s. As a result, very different microbial patterns end up grouped under the same diagnosis.

That lack of detail matters. Clinically, people with BV don’t all have the same symptoms, the same recurrence patterns, or the same response to treatment. Some people feel better quickly but relapse soon after, while others improve for longer stretches of time. These differences suggest that BV isn’t one uniform condition, but a collection of different microbial states that we’ve been treating as if they were all the same.

What Evvy’s research found

By using high-resolution DNA sequencing on vaginal microbiome samples, Evvy’s researchers were able to identify several distinct microbial patterns within BV. These patterns represent different “types” of BV at the microbiome level — not separate diseases, but different versions of the same diagnosis with different bacterial makeups and behaviors.

Here are the main BV Subtypes Evvy’s research identified:

The key takeaway is that BV isn’t one-size-fits-all. When we treat all BV cases as if they’re biologically identical, we shouldn’t be surprised that results are inconsistent. Different microbial patterns are likely to respond differently to the same treatment.

What this means for you

For years, BV research and treatment outcomes have looked messy and unpredictable. Some treatments seem effective in studies, but people’s real-life experiences vary widely. One reason is that studies have traditionally grouped together people with very different underlying microbiomes and analyzed them as if they were one homogeneous group.

By breaking BV down into clear microbial subtypes, this research creates a way to study recurrence, symptoms, and treatment response within biologically similar groups. That’s a huge step toward understanding why BV comes back for some people, why it lingers for others, and why certain approaches may work better in some cases than others. 

These BV Subtypes are now integrated into the Evvy experience. People who take Evvy’s at-home vaginal microbiome test and receive a BV result will see which subtype best matches their microbiome, along with clear education and access to clinician-designed care pathways when eligible. This added layer of insight is designed to complement existing clinical diagnostic criteria (not replace them) by providing a clearer picture of the underlying biology behind a BV diagnosis.

Once biological differences become measurable, they become actionable. By bringing modern microbiome science into BV care, this research lays the groundwork for more precise studies, more effective treatments, and ultimately better reproductive health outcomes. Evvy has shared the methodology behind this research and plans to publish larger studies that explore how these BV Subtypes relate to symptoms, recurrence, and treatment durability.