Introduction and Aim

Have you ever wondered why some vaccines aren’t as effective in certain parts of the world, especially in low-income countries? For instance, the current rotavirus vaccine given orally to babies in countries like India, Indonesia, and parts of Africa tend to be less effective or only works in a smaller proportion of babies compared to those in high-income countries.

Scientists at the Murdoch Children’s Research Institute in Australia, have developed, a new oral Rotavirus vaccine called RV3-BB. This vaccine has some unique advantages: it is based on unusual type of rotavirus that is found naturally in newborn babies but doesn’t cause diarrhea so it is safe and provides very good protection from severe rotavirus disease when given at birth. The existing oral rotavirus vaccines, RotaTeq and Rotarix, are administered only from 6 weeks of age.

Recent studies have shown that giving a birth dose of a rotavirus vaccine may have important advantages to optimise protection for children living in high child mortality regions when compared to giving the vaccine later. But as scientists, we can’t stop here. We wanted to understand why a birth dose of an oral rotavirus vaccine might work better to prevent severe diarrhea caused by rotavirus infection, particularly in low-income countries. This is the focus of our latest study, recently published in Nature Communications. In this research, we analysed the gut microbiome—the bacterial world in babies' stools—using advanced sequencing techniques and bioinformatics tools. Understanding the interaction between the gut microbiome and the protection provided by a rotavirus vaccine is key to ensuring the success of rotavirus vaccines globally.

How Did We Conduct the Research?

We collected stool samples from nearly 300 babies in Malawi and Indonesia, splitting them into two groups. One group received the vaccine at birth, while the other received the first dose at 6 weeks of age. All babies received a total of 3 doses of the RV3-BB vaccine. We measured the response to the vaccine and by, also analysing the babies' stools, compared the impact of gut bacterial communities present in each group. Human stool samples contain a complex mix of bacteria and viruses, and studying these microbial communities has long been a valuable tool in understanding diseases like diabetes and various gut disorders.

Key Findings and Their Significance

One of our most exciting discoveries was that babies who had a positive vaccine response after receiving the RV 3-BB vaccine at birth showed higher bacterial diversity in their gut microbiomes. High bacterial diversity generally is associated with a “healthy” microbiome. Consistent with this finding, “beneficial” bacteria like Bacteroides were also associated with a positive vaccine response. On the other hand, certain disease-causing bacteria, like Streptococcus and Staphylococcus, were linked to a negative vaccine response. These findings suggest that the RV3-BB vaccine, when given at birth, may help shape the early gut microbiome in a way that improves the body’s response to a rotavirus vaccine. Also that RV3BB vaccine given at birth, may offer a unique opportunity to optimize protection against severe rotavirus disease.

Why This Research Matters

Our research helps bridge the gap in understanding why some vaccines perform better in certain geographical settings, such as is observed in children living in high-income versus low-income countries. By studying how the gut microbiome influences the response to rotavirus vaccines, we can develop better ways to prevent the death and disease due to rotavirus infection that work for the world’s children, especially the most vulnerable—young children in low-income countries.

Thank you for your interest in our research!