Three years ago, we launched our call to make history with Isala. And we definitely did that together more than 6000 women! As researchers at the University of Antwerp, we are extremely proud of what we have achieved so far with Isala. We have a unique set of data to further investigate the vaginal microbiome of healthy women in Belgium and abroad. On this page, you can find an overview of the main results of our research.

Since 2020, we have learned and discovered a lot, so we are building this page based on the questions you might have. You can look for the information that interests you the most, or just read all of it! 😊


Who took part in Isala so far? 

The participants in Isala are in good company! In our home country Belgium, more than 6000 women registered for the first phase of Isala of which 3300 women also donated a set of vaginal swabs. The youngest woman was 18 years old, the oldest no less than 98. Of this large cohort, 1921 participants had been pregnant at least once, and all women from Isala together identify with at least 99 diverse cultures. As scientists, we remain very careful with the interpretation of all research data. In 2022, there are still barriers for parts of the population in Belgium and abroad to participate in citizen science projects. But Isala is also actively working on removing those barriers for future citizen science projects, especially those with an intimate kind like ours. So, we are making history with that too! And as mentioned before, we are actively working on diverse sisterhood projects across the world. For example, in Peru,  more than 100 women from the Amazon and Coastal regions have already provided samples. In addition, 110 women from the Highlands will provide samples in the coming months. Our little Isala sister in Peru was named Laura. Here you can read how it started and an update is coming soon!

We find it very important to recruit and communicate as inclusively as possible. Our broad aim is to focus on women’s health. But at Isala, we do hope that everyone feels welcome and recognized. In case you do not feel this way, know we appreciate all feedback and suggestions, feel free to get in touch with us. In future phases of research, we will continue to try to recruit as diverse and inclusive as possible. For example, people who do not identify as women but do have a vagina are very welcome to be part of our research. 

A couple of months after this first research phase of Isala in Belgium, a second phase has followed. There are indications that the vaginal microbiome is dynamic, even fluctuating within one menstrual cycle. To test this hypothesis, the Isala team selected 275 women from the first Belgian cohort. These women were invited to collect six vaginal swabs over the course of two menstrual cycles. They also collected skin and saliva swabs. All much-needed data to determine how the vaginal microbiome evolves and what influencing factors exist – in the short and long term.

What happened already with all the swabs?  

In the spring of 2020, the Belgian Isala participants were asked to collect two vaginal swabs at home: a blue and a pink swab. Back in the days, we were all not as familiar with swabs as we are now after taking several covid self-tests. Therefore, we found it very important to provide enough information and give our participants the confidence to collect the swabs themselves. Isala hopes this way to empower women to literally take their health into their own hands.

The Isala swabs do not work in the same way as the covid self-tests. The fluid in the blue swab serves to protect the microbial DNA on their way to the lab and helped us identify the most numerous types of bacteria in your vagina, using high-tech DNA analysis. This high-tech DNA analysis is quite a complex form of research. For example, suppose you have a pap smear taken at the gynecologist. In that case, this is usually only checked via a PCR test for the human papillomavirus and examined under the microscope to look for abnormal human cells. We have gone a step further to fully map the entire vaginal microbiome.

We use the pink swab to grow live bacteria. During processing, the liquid from the swab is gently applied to the growth medium in a Petri dish. After a couple of days, we check whether the bacteria have grown enough to be visible to the naked eye. In that case, we can further investigate the bacteria in the lab. This is a major step in our research, since we can learn a lot more about their positive properties for female health. For example, we think that some bacteria could eventually help as an alternative to antibiotics in women who suffer from infections, inflammation or other discomforts. Up to now, we have already been able to culture more than 2000 different vaginal bacteria – a momentous success! – and this number will still grow over the following months.

Which bacteria were already found?

All samples that we receive within the Isala framework are intensely analyzed by the Isala researchers. The first phase of our Isala project in Belgium was the first time that vaginal samples were collected from healthy women at such a large scale globally. Of course, we already knew a lot about the composition of the vaginal microbiome. However, until Isala, most samples had been taken in a medical context by women with health complaints. Now, for the first time, we have a large set of samples from a general, healthy Western-European population. Also the Peruvian samples were donated by healthy women in the privacy of their homes with the guidance of a health care worker. Thanks to Isala, we found that around 80% of the Belgian participants have a vaginal microbiome dominated by lactic acid bacteria, with lactobacilli being the most common.These bacteria are associated with a healthy vagina based on published scientific studies. The results from the Peruvian cohort are expected very soon. We are curious whether we will also find a dominance for lactobacilli.

To present this large amount of information clearly, we initially chose to focus on the eight most important bacteria among all participants. These are Lactobacillus crispatus, Lactobacillus iners, Lactobacillus jensenii, Lactobacillus gasseri, Gardnerella vaginalis, Prevotella, Bifidobacterium and Streptococcus. We as researchers appointed each woman to one of these eight types, which means that this bacterium was the most common one of the eight in their swab. But that was not the only bacterium we found in their swab since the composition of each microbiome is unique. That is why, in addition to the dominant type, each Isala participant also received a table in which we give the percentages of the eight most common bacteria. Over the course of 2021, we discovered that there are two more bacteria that we would like to add to the list of eight. That’s why we updated our overview in the summer of 2022: Limosilactobacillus and Anaerococcus also received their own vaginal passport. Limosilactobacillus was first categorized in the group “other type of bacteria”, since their concentrations were much lower than the 8 most common bacteria. More analyses clarified that this bacterium occurs very often with other lactobacilli, which makes us suspect that these bacteria all work together to keep the vaginal ecosystem in balance, with Limosilactobacillus potentially as an important driving force. We also found that Anaerococcus  appears to play an important role in the vaginal microbiome, but the extent of that role remains to be determined. Nevertheless, it also deserves a place on our wall of fame.

Here they are – the ten most important bacteria that the researchers currently found in the Isala participants:

Lactobacillus crispatus
Lactobacillus iners
Lactobacillus jensenii
Lactobacillus gasseri

During the communication of the personal results in the summer of 2021, all participants received a unique profile with the composition of their vaginal microbiome. All these profiles are now updated, also containing the percentages of Limosilactobacillus and Anaerococcus found in the swab.

Lactic acid bacteria or lactobacilli, where do I know them from?

You probably recognize them from your morning yoghurt! They are indeed related to the bacteria you can find in yoghurts. Lactic acid bacteria are those bacteria that convert the natural sugars in milk into lactic acid during fermentation. As a result, yoghurt has a more acidic taste and is thicker in texture. 

In more than 80% of the swabs we analyzed at Isala, a lactic acid bacterium, in particular a Lactobacillus, was dominant. In the vagina, these bacteria actually do the same thing as in yoghurt. Because they will use glycogen, a type of sugar that is also in the wall of the vagina and uterus, as a nutrient and convert it into lactic acid. Therefore, thanks to the lactobacilli, a healthy vagina has a low acidity, which is extremely important in the fight against pathogenic bacteria or viruses. 

Lactobacilli are not only found in the vagina. They are also often found in the intestines, on the skin or even in one’s nose. The four most common types of lactobacilli found in Isala – Lactobacillus crispatus, Lactobacillus jensenii, Lactobacillus gasseri and Lactobacillus iners – are also found on our skin, for example in the groin area.

Thanks to the blue swabs, we know which lactobacilli are present in the vaginas of women in Belgium. And thanks to the pink swabs we can also culture these special bacteria to further investigate their properties. This is, however, easier said than done. We try to mimic the conditions in the vagina in the lab the best we can, but a Petri dish remains very different from an actual vagina. Some bacteria are so specifically adapted to living in the vagina that they have difficulties surviving in other environments.

We are immensely proud to tell you that we are already learning a lot about the cultured bacteria and their functions. A few lactobacilli can for example produce riboflavin (also known as vitamin B2). Then there are strains that produce special tiny proteins that stop the growth of bad bacteria, or that can arm the vagina against fungal infections. All these discoveries are important and truly pioneering research. They do not only make us understand the composition of the vaginal microbiome better, but they also form the foundation of potential new therapies. We really hope that one day, based on Isala, novel living therapeutics can help women get and keep their vaginas healthy.

How many different bacteria are already found?  

Way too many to mention! :)   

Because even within the same Lactobacillus species, there can still be a lot of variations in their genetic code. We then call these variants different strains or isolates of the same species. You can compare this to the different variants of the coronavirus, that we learned a lot about over the past years.  

Every vagina contains a unique combination of different strains, together making up billions of cells. The Isala results we have so far were mapped on large graphs to enable us to see patterns. Each Isala participant is one anonymous line or dot and forms a small piece of the whole puzzle. The analysis of all swabs gives a nice graph with a kind of continuum. It is not a question of whether that bacterium or another, rather a story of more and less. There is no single vagina that contains only one type of bacteria. It is always a combination of different types that determine your unique vaginal microbiome.

We then determined for each participant the percentages of the 10 bacteria in the swabs. This graph summarizes the whole of Isala; each vertical line is the bacterial composition in the vagina of one woman who has taken a swab for Isala: 

Which patterns among all these bacteria were observed ?

Well, that is an interesting question with an interesting answer!

During the analyses we indeed noticed that some strains or species of bacteria seemed to occur together very often, or were less likely to occur together. For example, we found Lactobacillus crispatus, Lactobacillus jensenii and the Limosilactobacillus often together. We suspect that these bacteria somehow work together and help each other to survive.

The discovery that we found these three specific types of lactobacilli – we already call them the Isala crew – occur together so often. This becomes even more interesting when you know that these bacteria are often associated with a healthy vagina in published scientific studies. The link between vaginal health and these Lactobacillus crispatus, Lactobacillus jensenii and Limosilactobacillus can probably be explained by the fact that they really function like little factories and start producing substances themselves such as lactic acid and other protective or useful molecules that they can also pass on to each other. To confirm this, further lab research is needed, and we are working very hard on this. We have observed the same association in another large collection of studies – the VALENCIA dataset – which tells us that this relationship is not unique to the Belgian participants in Isala.

Does the vaginal microbiome stay the same all the time?

No, based on the first analyses of all blue swabs from the first research phase at Isala, we could already deduce that there are many factors that influence the composition of the microbiome in the vagina in the short or long term. But in order to investigate this properly, we needed multiple samples over different cycles from the same women. And that is exactly what Isala asked of the participants in the second Belgian research phase. Again, the commitment of our participants was fantastic, and the samples quickly found their way to our lab.

The first thing we wanted to know was whether the composition of the vaginal microbiome could change significantly in a few months’ time. Most participants, about 70%, had the same dominant bacteria in the swabs of both research phases. In the other participants the dominant bacterium did change. Often this new dominant bacterium was already present in the vaginal microbiome of the first phase of the study. The stability was especially high for women with lactobacilli. To give a concrete example, women who were dominated by Lactobacillus crispatus in the first phase had an 88% chance that this was also the case in the second research phase, months later.

Participants who had a less favorable profile and who were dominated by Gardnerella in the first swab, for example, had a 62% chance that this dominance had disappeared in the second swab. We therefore repeat that, certainly when you had a slightly less favorable result, it is quite possible that the composition of your microbiome has changed in the meantime. This discovery seems good news for the stability of healthy vaginas, but again, further research is needed to draw definitive conclusions. And we keep repeating this: if you experience any complaints, it is best to consult your doctor.

What factors influence the vaginal microbiome?

Thanks to the pioneering research of Isala, we know that the vaginal microbiome can change, and we also know more about which bacteria indicate a healthy microbiome. So then the next, very legitimate question is: what factors influence the microbiome and can I do things myself to keep my vagina healthy or make it healthier? Remember however that a vagina is basically a self-cleaning organ and keeps itself and their microbes in balance.

To find the answers to these questions, we asked more than 166 questions in Belgium and 71 in Peru via several surveys to our participants. But the statistical analysis of all these data is complex and we do not want to jump to conclusions. With Isala, we are making history, because it is the very first time that information about their vaginal microbiome has been collected from such a large group of healthy women. But writing history is also pioneering work, of course. We want to be sure that the links we find are also causal links and that there are no other factors that could explain it.

So, we already want to say clearly that we are far from finished with this research and that we want to carry out many more analyses in the coming months and years. Our biostatisticians know what to do. 😉

But of course, we have already found some factors that we are certain have an influence on the composition of the vaginal microbiome, so we would like to share these:


We now know for sure that the vaginal microbiome changes with age. One of the main reasons for this is the hormone levels that change throughout every woman’s life. The most drastic changes are of course during puberty and menopause. This was also seen in our data: the vaginal microbiome of Isala menopausal women was indeed often more diverse, and more dominated by Prevotella and Anaerococcus and less by lactobacilli.

The youngest participant in Isala was 18 years old, so conclusions about the impact of puberty are awaiting follow-up research.

Whether or not you have children

The Isala researchers had expected age to have a significant impact on the microbiome. A bigger surprise was that, of all the factors we studied, having or not having children came out on top as the second most important explanatory factor. Women with children – even after early pregnancy loss, abortion or stillbirth more often have Bifidobacterium and Streptococcus in their vagina, whereas we found Lactobacillus crispatus more often in women without children.
This is not due to the fact that women with children are on average older than women without children – in this analysis we corrected for age, so we took that into account.  At Isala, we consider this a truly groundbreaking finding, although we are not yet sure how to explain it. What changes during and after a pregnancy? And how long do the effects last? What role does Bifidobacterium play exactly? Is this bacterium perhaps as beneficial as the lactobacilli that we already know much more about? Why do these changes leave their traces in the vaginal microbiome for so long? These are all questions that are on our list for follow-up research at Isala.

Your menstrual cycle

That hormones have a major impact on the composition of the vaginal microbiome is something we at Isala expected, but the influence is also very strong in the short term. Did you know that during the menstrual cycle, women’s hormone levels fluctuate greatly? This is something that is unique to humans and different from most animal species.

We will give you a short recap, because we have noticed that many people – including ourselves – are not very familiar with this natural cycle:
– Follicular phase: from your period until ovulation, the estrogen level rises very sharply and your body prepares an egg.
– Ovulation: You are now fertile, and the estrogen level takes a dive.
– Luteal phase: a rise in progesterone followed by a fall in both hormones until just before your period starts.
In this blog, you can find more details about the natural cycle.
Interestingly, these distinct phases of the menstrual cycle play a role in the composition of the microbiome. Women who took their swab in the week after their period had a more diverse microbiome with more different bacteria. Women who took their swab later in their cycle often had less diverse bacteria. How exactly a woman’s microbiome changes under the influence of the successive phases of her cycle will be further investigated with the samples collected during the second phase of Isala. But we already know that the impact is big.

Hormonal contraception

If the natural hormones in your body can have such an impact on the composition of the vaginal microbiome, it is not surprising that hormonal contraception has an impact too. For example, according to our research, taking the combined pill (with estrogen and progesterone) results in less Gardnerella and Prevotella and more lactobacilli in your vaginal microbiome.
In the vaginal microbiome women using a hormonal IUD, on the other hand, we found more Gardnerella. Maybe of interest to you if you are making choices for your own contraceptive method. Of course, other factors play a role in these effects, so we want to investigate further whether these are indeed causal links. In any case, the choice is very personal and depends on much more than your microbiome. If you would like more information on this subject, be sure to check out this website.

Choice of period products

It’s not all determined by hormones only, we also found that the type of menstrual product you use has an impact on your microbiome. It was particularly noticeable that after using sanitary pads the microbiome is more diverse, with more Bifidobacterium, Lactobacillus gasseri, Streptococcus and Anaerococcus. Conversely, after using a menstrual cup, we found more Lactobacillus crispatus and Limosilactobacillus. This is certainly an interesting insight into the development of all kinds of new hygiene products. For menstrual underwear or tampons, we have not yet found any clear effects, but it is certainly something that we want to investigate further. Just like the material of underwear. Because there might be big differences between cotton, synthetic materials, bamboo, …

Sexual activity

Sexual activity also has an impact on the vaginal microbiome. In the participants who had sex in the 24 hours before taking their swab, we found more diverse bacteria more often. Streptococcus, for example, was one we found more often. This result is very interesting for the GeneDoe research that, as daughter project of Isala, investigates the forensic application of microbiome research in sexual violence cases. Here you can read more about GeneDoe. 

Eating and drinking

Thanks to the extensive questionnaires that all Belgian Isala participants completed, we were also able to investigate less obvious links. For example, we observed that sugary drinks, vegetables, probiotics, alcohol, fish and meat all have an significant link with composition of your microbiome.

Sugar-sweetened drinks and meat appeared more likely to have a negative impact, whereas vegetables or nuts might help to create a healthier vagina. We are planning a lot more follow-up research on this at Isala in Belgium and abroad, because it is quite impressive that we there might be a link with eating habits that is not only linked to your weight. For example, they might also have direct consequences for your vaginal health, and it will be important to investigate this across the world for diverse food habits. However, to prove such a direct link, we will need to perform more focused (intervention) studies that will allow us to make any conclusions or recommendation that you might be able to change your microbiome with foods.

Why did you also examine the bacteria on the skin and in the mouth? 

To get a more complete picture of the microbiome of women in Flanders, the microbiome of the skin and mouth were examined in addition to the vagina. We asked the participants to take a swab of the skin around the mouth, of their saliva, around the breast and of the groin area. After all, these areas have barely been studied and they are relevant to female health, intimacy and sexuality and contact with underwear and clothes. On the results page, you can check which bacteria were found on the skin and in the mouth. It probably won’t surprise you that all those places on your body had a different microbiome, since they come into contact with different things.

What did you discover about the bacteria in our saliva?

In the saliva, we detected a surprisingly stable salivary microbiome that was very similar across all participants. This core microbiome consists of eight genera of bacteria found in more than 98% of all women studied. This does not mean that all these bacteria are exactly the same, because within genera of bacteria there are still many different species and strains. Just as within a family genus in people with the same surname there are many different individuals. We already use very advanced techniques at Isala to do all the analyses, but it is still not possible to distinguish between all those different species. Further research may follow in the next few years, but for now it is already very interesting to see that we saw the same genera of bacteria coming back again and again, often even in similar proportions. As with the vaginal swabs, we very carefully determined the percentages of these eight types of bacteria in our analyses. This graph summarises it all: each vertical line represents one woman who took a saliva sample for Isala. Each colour represents a bacterial genus, with the percentage of this bacterial genus within the total microbiome on the left axis:

You can see that almost every vertical line that you can draw – so each time the result of one of our participants – has the eight different colours. That’s the core microbiome that we found in all the saliva samples from Isala.  

You don’t have these bacteria in your saliva from birth. This salivary microbiome really starts to develop at the time of the first teething. The specific species and variants of those eight genera of bacteria that will settle down may be a little different in each individual…. It still changes significantly until infancy; after that, the changes are rather subtle. Still, we know from previous research that there are a number of factors that can influence the microbiome of your saliva, for example taking medication (like antibiotics), smoking, obesity, cavities in your teeth…

Thanks to all the data we already collected on our participants at Isala based on the extensive surveys, we were also able to examine factors such as contraception and sexual habits. We found in both cases no clear association with the composition of the microbiome of your saliva. We did find that having bleeding gums and consuming fermented beverages and yoghurt had an impact on the occurrence of some bacteria of the core microbiome.

Which bacteria did you find on the skin around the mouth?

At Isala, we went above and beyond and examined the microbiome of the skin around your mouth as well. As expected, we saw a clear overlap between different genera of bacteria in both the saliva and the skin around the mouth, such as Actinobacillus, Neisseria, Veillonella, Prevotella and Streptococcus. Besides, of course, the occurrence of typical skin bacteria such as Staphylococcus.

What did you discover about the bacteria on the intimate skin areas, around the breasts and the groin?

On the groin skin, we found a lot of typical skin bacteria such as Staphylocccus and Corynebacterium, but also bacteria that we previously saw as vaginal bacteria such as Lactobacillus crispatus, Lactobacillus iners and Prevotella. Lactobacillus crispatus and Lactobacillus iners are typical vaginal bacteria that we also found on the groin skin. Interestingly, we also found these bacteria on the skin around the breasts (in 41% we found Lactobacillus iners and in 53% Lactobacillus crispatus). 

Our research group previously studied the skin microbiome of the face. Then, we also found lactobacilli such as Lactobacillus crispatus and Lactobacillus iners. Lactobacilli are the first bacteria that colonise a baby during natural childbirth. Still, the presence of for example Lactobacillus iners on the skin was rather unexpected, as they are not well adapted to grow outside the vagina.  It is also possible that these bacterial species occur here due to having intimate contact. Further research will reveal whether these are on the skin through brief contact or whether they can really survive on these skin zones.

The three examined zones of the skin also showed similarities. For example, four bacterial genera were found on all three skin zones examined. In this graph, you can discover the overlap between the different zones and on the skin bacteria results page you can clearly see which bacteria were found where.

Were there big differences between the skin microbiome of the different participants? 

Quite a bit, especially if we compare it with the salivary microbiome we recovered. Although there is one bacterial genus, Staphylococcus, that we really saw in every participant. We also made summary graphs for the skin microbiome, with each vertical line representing the result for one participant. We are happy to give them to you for completeness:

How can this knowledge be used in the future? 

Isala’s dataset is undoubtedly unique. The researchers intend to conduct many more in-depth analyses and follow-up studies in the coming months and years, because the fascinating world of female health still holds many secrets that are continuously unravelled thanks to Isala’s pioneering research. Thanks to the sister projects already launched in Peru, Switzerland, Cameroon, UK, Spain, Uganda, Marocco etc, the research is even transcending borders.

But at Isala, we would like to go a step further and see if our microbiome analyses could also contribute as evidence in sexual assault cases. This project from Isala falls under our daughter project GeneDoe. Keep following Isala’s channels to know more about this exciting research. If you are already keen to read more, you can take a look at our GeneDoe blog posts.

Is the research finished now? 

No, not at all! 

As Isala researchers of the University of Antwerp, we are already very satisfied with the results. We did not expect that no less than 80% of the vaginas studied would be dominated by lactic acid bacteria, because based on the literature we had estimated this to be lower. We now want to investigate this across the world. Isala is increasingly recognized by the international scientific community as an important and innovative pioneer in female health. We speak at conferences, write papers and inspire scientists all over the world. In Peru (the Laura project) and Switzerland (the Marie project), concrete follow-up studies by Isala are ongoing or being set up. So hopefully Isala can have sisters all over the world who will write history together.

In the coming years, we also want to further deepen our knowledge of the composition of the vaginal microbiome and continue to analyze and test which factors have the greatest impact on a healthy vagina. The first steps have been taken, but we really want to work out concrete recommendations and tips so that women can take their health (even) more into their own hands. Because of course you know that the choices you make every day have an impact on your health, but it is surprising and a groundbreaking discovery that there also seems to be such a direct relationship between, for example, your eating habits and the health of your vagina.

In the years to come, Isala not only wants to help women become more aware of their own vaginal health, but hopefully all the knowledge about the cultured bacteria will also help to develop medicines that help women with problems. Medicines based on living, healthy bacteria, so no antibiotics but probiotics!

There are still exciting years ahead, because of course we are sure that there are many other factors that determine how healthy your vagina is. Think about genetics, general immunity, or a certain disease for example. Before the end of 2022, for example, we will be looking at Belgian women who live under the same roof (sisters, partners, mothers and daughters, friends, …) to see if women who live together also have a similar vaginal microbiome. We also aim to diversify our study cohort considerably. To achieve this, we are working closely with the sociologists from the Isala advisory board by organizing focus groups, in-depth interviews and surveys. All suggestions to help Isala to be more diverse and inclusive are very welcome.

Every step we can take with Isala is a step towards more knowledge, more understanding and more attention to female health. And we are very happy that such a wonderful, enthusiastic community is walking with us. Thank you!