Kate McLean, MD, MPH, FACOG: Better understanding bacterial vaginosis

The scientific understanding of bacterial vaginosis (BV) is evolving rapidly, with advances in microbiome sequencing and new evidence on sexual transmission prompting a closer look at a condition long considered straightforward, according to Kate McLean, MD, MPH, FACOG, OB-GYN, Chief Medical Officer, Evvy.

In this Contemporary OB/GYN video interview, McLean discussed how the field is beginning to move toward a more granular understanding of the most common vaginal condition in the United States, which impacts more than 30% of reproductive-aged women annually, according to Evvy and the Centers for Disease Control and Prevention.^1,2

Several microbes are part of BV

"We spent a long time oversimplifying BV, and I would say that even the standard of care, unfortunately, now, is to oversimplify BV," she said. "For example, many of the standard of care tests to diagnose BV only look for a small handful of microbes that can potentially cause BV, when we actually know there is a very, very long list of microbes that can work together to cause BV,” said McLean. “We also know that the degree to which somebody has symptoms from BV may depend not just on which microbes are present, but in what amounts they are present, and [whether] there [are] also healthy microbes."

She noted the recognized protective role of certain lactobacilli. "This type of microbe, these Lactobacilli, Lactobacillus crispatus specifically, are not going to be a surprise to the medical community to hear me mention them, they are recognized as being the heroes of the vaginal ecosystem, keeping things healthy," McLean said, adding that standard testing does not fully account for the balance between harmful and protective bacteria.

In February, Evvy announced data identifying 6 distinct microbial subtypes among patients clinically diagnosed with BV, drawn from shotgun metagenomic sequencing of more than 100,000 vaginal microbiome samples. The company positions the subtypes as complementary to, not a replacement for, established clinical diagnostic criteria.

Can BV be transmitted through sexual transmission?

McLean also pointed to a shift in understanding of how BV spreads.

"For so many decades we did not recognize that BV could be sexually transmitted, and that has really only changed in the last year or so," she said. "There was a landmark paper that came out in the New England Journal of Medicine that demonstrated that treating male partners for BV at the time when their female got treated actually dramatically reduced recurrence, and so now we are starting to really understand that what our patients were telling us for a long time about BV being sexually associated is now scientifically proven in that regard."

McLean characterized the field as still evolving. The science remains at an early, cutting-edge stage, she noted, and continued research will be needed to translate emerging microbiome insights into improved treatment and recurrence prevention.

References:

1. Evvy Unveils Data-Driven Subtypes of Bacterial Vaginosis. Evvy. Press release. Published February 26, 2026. Accessed July 1, 2026. https://www.businesswire.com/news/home/20260226236249/en/Evvy-Unveils-Data-Driven-Subtypes-of-Bacterial-Vaginosis
2. About Bacterial Vaginosis (BV). CDC. Accessed July 1, 2026. https://www.cdc.gov/bacterial-vaginosis/about/index.html