Babies born vaginally have a different microbiome to those born by Caesarean section and have heightened responses to childhood vaccinations, according to a new study heralded as “interesting and important” by experts.
The microbiome is known to play a role in immune responses to vaccination. However, the relationship between early-life effects on intestinal microbiota composition and subsequent childhood vaccine responses had remained poorly understood. In the new study, “the findings suggest that vaginal birthing resulted in a microbiota composition associated with an increase in a specific type of antibody response to two routine childhood vaccines in healthy babies, compared with Caesarean section,” the authors said.
Researchers from the University of Edinburgh, with colleagues at Spaarne Hospital and University Medical Centre in Utrecht, and the National Institute for Public Health and the Environment in The Netherlands, tracked the development of the gut microbiome in a cohort of 120 healthy, full-term infants and assessed their antibody levels following two common childhood vaccinations.
The study, published in Nature Communications, found “a clear relationship between microbes in the gut of those babies and levels of antibodies.” Not only was vaginal birth associated with increased levels of Bifidobacterium and Escherichia coli in the gut microbiome in the first months of life but also with higher IgG antibody responses against both pneumococcal and meningococcal vaccines.
Antibody responses doubled after vaginal birth
The babies were given pneumococcal and meningococcal vaccinations at 8 and 12 weeks, and saliva was collected at follow-up visits at ages 12 and 18 months for antibody measurement. In the 101 babies tested for pneumococcal antibodies, the researchers found that antibody levels were twice as high among babies delivered naturally, compared with those delivered by C-section. High levels of two gut bacteria in particular – Bifidobacterium and E. coli – were associated with high antibody responses to the pneumococcal vaccine, showing that the microbiome mediated the link between mode of delivery and pneumococcal vaccine responses.
In 66 babies tested for anti-meningococcal antibodies, antibodies were 1.7 times higher for vaginally-born babies than those delivered via C-section, and high antibody levels were particularly associated with high levels of E. coli in the babies’ microbiome.
The results were also influenced by breast-feeding, which even among children born vaginally was linked with 3.5 times higher pneumococcal antibody levels, compared with those of formula-fed children. In contrast, levels of antibodies against meningococcus were unaffected by breast-feeding status.
Microbiome ‘sets level of infection protection’
The team said: “The baby acquires Bifidobacterium and E. coli bacteria through natural birth, and human milk is needed to provide the sugars for these bacteria to thrive on.” They explained: “The gut microbiome is seeded at birth, developing rapidly over the first few months of life, and is influenced mostly by delivery mode, breast-feeding, and antibiotic use.” The babies’ microbiome in early life contributes the immune system’s response to vaccines, they said, “and sets the level of protection against certain infections in childhood.”
Study lead Professor Debby Bogaert, chair of pediatric medicine at the University of Edinburgh, said: “I think it is especially interesting that we identified several beneficial microbes to be the link between mode of delivery and vaccine responses. In the future, we may be able to supplement those bacteria to children born by C-section shortly after birth through – for example, mother-to-baby ‘fecal transplants’ or the use of specifically designed probiotics.”
First author Dr. Emma de Koff, a microbiology trainee at the Amsterdam University Medical Center, said: “We expected to find a link between the gut microbiome and the babies’ vaccine responses, however we never thought to find the strongest effects in the first weeks of life.”
The findings “could help to inform conversations about C-sections between expectant mothers and their doctors,” commented the researchers, who said that they could also “shape the design of more tailored vaccination programs.” For example, in the future, vaccination schedules could be adjusted based on the method of delivery or analysis of the baby’s microbiome.