New study reveals key to long-term vaginal microbiome balance with just a few samples

A new study published in Microbiome by researchers at Karolinska Institutet, suggests that a few well-timed samples could help predict long-term imbalances in vaginal health, which is linked to various health issues.

The vaginal microbiome fluctuates during the menstrual cycle, with some women maintaining balance while others shift toward imbalance. This study tracked 49 women daily through a cycle using metagenomic sequencing, identifying four Vaginal Community Dynamics (VCDs): constant eubiotic, constant dysbiotic, menses-related, and unstable dysbiotic.

Higher bacteriophage levels and specific bacterial genes were linked to instability. The study suggests that just a few well-timed samples could help predict long-term imbalances, offering a novel tool (VALODY) for assessing vaginal health.

“This novel framework provides a more detailed view of the vaginal microbiome and its fluctuations, revealing the importance of phage activity and genetic factors in maintaining or disrupting balance.

“Just a few well-timed samples could help clinicians predict whether a patient is at risk of long-term dysbiosis, which is linked to increased risk of sexually transmitted infections, fertility treatment failure, pre-term birth, and gynecological cancers,” says Ina Schuppe Koistinen, author and researcher at the Department of Microbiology, Tumor and Cell Biology at Karolinska Institutet.

In this collaborative study, both molecular and clinical science were combined to propose a new classification system to understand the dynamics of the vaginal microbiota. The study was conducted in collaboration with Prof Henriette Svarre Nielsen at the University of Copenhagen.

A cohort of healthy young women was asked to collect daily vaginal samples and fill in a short questionnaire throughout one full menstrual cycle. The microbiome composition of the samples was analyzed at the Center of Translational Microbiome Research at Karolinska Institutet.

“In the future, this model could guide personalized approaches to managing women’s health and help understand the role of transient versus persistent microbiome imbalances in conditions like bacterial vaginosis,” says Schuppe Koistinen.