Women's health has long been overlooked in science and medicine-an oversight with serious consequences not just for women, but for public health as a whole. A 2024 McKinsey report found that women spend 25% more time in "poor health" compared to men, due, in part, to diagnostic delays, lack of tailored treatments and historic underinvestment in conditions that primarily or disproportionately affect women. 
"We know that if we increase the health of women, we are increasing the health of our communities because women give birth to all of humanity," said Melissa Herbst-Kralovetz, Ph.D., professor at the University of Arizona College of Medicine-Phoenix and Director of the Women's Health Research Program and Microbiome Initiative.
Herbst-Kralovetz, who will be speaking during a session at ASM Microbe 2025 about host-microbe interactions in the female reproductive tract and their implications for gynecologic health and cancer, is part of a growing wave of scientists working to close the women's health gap-through data, research and a deeper understanding of the vaginal microbiome.
Do you study women's reproductive health? ASM Microbe is a great place to network with a global community of scientists exploring how microbiome composition and dysbiosis affect women's health across the lifespan.
The Vaginal Microbiome: A Key to Reproductive Health
One growing area of scientific interest that is transforming our understanding of women's health is the vaginal microbiome (VMB). Scientists are learning how this microbial ecosystem influences everything from infection risk and cancer to fertility and pregnancy.
A healthy VMB is typically dominated by Lactobacillus species. These rod-shaped bacteria help maintain a low pH and prevent the overgrowth of harmful pathogens. But when this delicate ecosystem becomes imbalanced, a state known as dysbiosis, the protective Lactobacilli are depleted and replaced by a diverse array of anaerobic and microaerophilic bacteria, such as Gardnerella, Fannyhessea, Prevotella and Sneathia. Depletion of Lactobacilli is associated with a greater susceptibility to bacterial vaginosis (BV), sexually transmitted infections, complications during pregnancy, endometriosis and even gynecologic cancer.
Herbst-Kralovetz and her colleagues are particularly interested in the VMB's role in cervical cancer, which is caused by persistent human papillomavirus (HPV) infection. "We know that HPV is the causative agent of cervical cancer," Herbst-Kralovetz explained. For 90% of women with HPV, the virus is cleared on its own, no problem. "So why do some women not clear HPV?"
What the VMB Reveals About Cervical Cancer
In Arizona, Hispanic women experience higher rates of cervical cancer compared to other races and ethnicities. To better understand why, Herbst-Kralovetz's team conducted a study of 100 premenopausal women- roughly 50% Hispanic, 50% non-Hispanic. They found that as Lactobacillus levels dropped, cervical abnormalities increased. Hispanic participants were more likely to have higher vaginal pH, less Lactobacillus dominance and more Sneathia bacteria, a genus implicated in reproductive disease. The team's study was the first to associate Sneathia abundance with all stages of cervical carcinogenesis, from initial HPV infection to precancer to cervical cancer.
These findings prompted the Herbst-Kralovetz Lab to conduct a global systematic review, led by undergraduate researcher Vianney Mancilla, of observational studies examining the VMB in Latina women and its relation to HPV and cervical cancer. Despite an extensive search across 2 major databases, they found only 25 studies published between 2000-2022 relevant to the research question, highlighting a major knowledge gap. Still, the team was able to identify bacteria in the cervicovaginal microbiome of Latina participants associated with HPV, cervical dysplasia and cervical cancer.
"One of the things we identified is that we need larger studies, but also more rigorous studies," Herbst-Kralovetz said. "But the outcome of examining those data was we did identify specific taxa that were more represented within the Hispanic [and Latina] populations and those also associated with cervical carcinogenesis." These differences in the VMB may be 1 factor behind the increased risk for cervical cancer among Hispanic and Latina women.
"Sneathia and Fannyhessea are the bugs that we're really interested in further exploring because we've identified them to be associated with different races, and then also ethnicity," said Herbst-Kralovetz.
What remains unclear, though, is whether these "bad" bugs are actively causing cancer or are simply "passengers along for the ride," as Herbst-Kralovetz put it. In other words, are they there because they thrive in the cancer-created microenvironment, or are they shaping the microenvironment to favor cancer? "That's the question we're still working to answer," she said.
Microbiomes, of course, don't exist in a vacuum. The VMB can be influenced by a wide range of factors, including housing stability, education level, access to health care services, hygienic practices (like douching) and more. Studies that explore how social determinants of health intersect with the VMB are essential for developing interventions that promote better health outcomes, especially for the populations most at risk.
Building a Future Where Women's Health Thrives
A healthier future for women starts with considering who is included in research, what questions are being asked and how health is measured across lifespan.
A key step is ensuring clinical trials reflect the populations they aim to serve. In the 1970s, the Food and Drug Administration (FDA) discouraged women of childbearing potential from participating in clinical trials for new medical products. This led to a lack of clarity about how U.S.-based treatments affected women. It wasn't until 1993 that a landmark law began requiring researchers to include more women and underrepresented racial and ethnic groups in biomedical and behavioral research.
But it shouldn't be just about improving numbers-it's also about how research is done and with whom. "Past harms and mistrust play a role in recruitment," Herbst-Kralovetz added. "It's really important that we do this work in an intentional way, in a community-based participatory research type of approach."
Her team is doing just that. In a pilot study on cervical cancer disparities among Native American women, they partnered with Native American Community Action (NACA), a wellness clinic in Flagstaff, Ariz., to recruit study participants. The study was part of the Partnership for Native American Cancer Prevention, a 25-year program between the U of A and Northern Arizona University (NAU) supported by the National Cancer Institute. Their current longitudinal study, conducted with MedStar Health and NAU, engages a research team composed mostly of Indigenous women and uses a "two-eyed seeing" framework that blends Western and Indigenous perspectives to co-interpret findings.
Equally important is collecting the right data. Capturing specific information leads to more accurate insights into how interventions affect different groups. Yet key elements of women's health, like menstrual cycles, are often missing from clinical studies.
"Even in large vaccine trials that were being done during COVID-19, studies didn't collect any information on menstrual cycles," Herbst-Kralovetz noted.
When individuals began reporting changes in their cycles after receiving COVID-19 vaccines, there were no data to refer to, fueling confusion and misinformation. A 2024 study analyzing data from reproductive-aged users of the Natural Cycles app later confirmed a small, short-term increase in cycle length (about 1 day), particularly when vaccination occurred during the follicular phase. The study's authors suggest that these cycle changes may stem from the close connection between the immune and reproductive systems, noting that certain signaling immune cells also influence the body's natural clock. While no link has been found between COVID-19 vaccination and fertility or pregnancy complications, the initial lack of data left a critical gap in public health messaging. This underscores the importance of collecting menstrual and vaginal health data to better understand how medical interventions affect women throughout life, including their impact on the VMB.
Then there's the issue of investment. In 2020, only 5% of global research and development (R&D) funding was allocated to women's health research, with just 1% supporting research into women-specific conditions unrelated to cancer. Of that, roughly 25% was dedicated solely to fertility. While public funding remains limited, momentum is continuing to grow. One example is the rise of FemTech (short for "female technology"), a term coined in 2016 by Clue founder Ida Tin to legitimize female health technology-enabled products, services and companies. This growing sector has directed private dollars into maternal health, menstrual products, gynecological devices and fertility solutions. Researchers like Herbst-Kralovetz are also advancing the field with support from private foundations. However, real progress demands long-term public investment and policy support.
In the case of cervical cancer, some nations show that significantly reducing and even eliminating cancer occurrence is within reach. Australia, for example, is on track to become the first country in the world to eradicate cervical cancer thanks to its National Strategy for the Elimination of Cervical Cancer and a $48.2 million investment to expand access to screening, follow-up services and better data access to target HPV vaccination efforts.
It's clear that the tools are there. What's needed now is collective action to finally close the gap.
Vaginal probiotics offer a concoction of vagina-friendly microbes-beyond the gut-friendly ones found in yogurts and kombucha. How effective are probiotics at boosting vaginal health and treating reproductive-tract infections?
