The relationship between gut microbes and antibody levels in 120 babies who were vaccinated at eight and 12 weeks against lung infections and meningitis were studied by researchers.
The study found double the antibody levels after the lung infection vaccination in the 101 babies who were "delivered naturally", compared with those delivered by C-section.
And the research team also found that for lung infection antibodies, breastfeeding was linked with 3.5 times higher antibody levels, compared with formula-fed children who had been delivered naturally.
Antibody levels after the meningitis vaccine were tested in 66 babies, and the experts found they were 1.7 times higher for “naturally delivered” babies, regardless of breastfeeding, compared with those delivered by C-section.
Prof Debby Bogaert, who led the study and is chairwoman of paediatric medicine at the University of Edinburgh, said it was “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 ‘faecal transplants’, or the use of specifically designed probiotics,” Prof Bogaert said.
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The research was carried out by a team from the University of Edinburgh, Spaarne Hospital and University Medical Centre in Utrecht, and the National Institute for Public Health and the Environment in The Netherlands. It was published on Tuesday.
The gut microbiome is seeded at birth, developing rapidly over the first few months of life, and is influenced mostly by delivery mode, breastfeeding and antibiotic use.
The team found a clear relationship between microbes in the gut of those babies and levels of antibodies.
For example, among a host of bacteria in the gut, high levels of two in particular — Bifidobacterium and E. Coli — were associated with a high antibody response to the vaccine that protects against lung infections.
High levels of E. Coli were also linked with a high antibody response to the vaccine that protects against meningitis.
The baby acquires the bacteria through “natural birth” and human milk is needed to provide the sugars for these bacteria to thrive on.
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The researchers said that babies’ microbiome in early life contributed to the immune system’s response to the vaccines, and set the level of protection against certain infections in childhood.
Experts have now said the findings could help to inform conversations about C-sections between expectant mothers and their doctors, and shape the design of more tailored vaccination programmes.
“We have known for quite some time that the mode of delivery is incredibly important when it comes to the type of bacteria which colonise our guts," said Dr Marie Lewis, a researcher in gut microbiota at the University of Reading.
“We also know that our gut bacteria in early life drive the development of our immune system, and natural births are linked with reduced risks of developing inflammatory conditions, such as asthma.
“It is therefore perhaps not really surprising that mode of delivery is also linked to responses to vaccinations.”
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Sheena Cruickshank, immunologist and professor in biomedical sciences at the University of Manchester, said: “Whilst this is an interesting study that adds to our knowledge of how the microbiome develops and the possible implications for immune development, it is still very preliminary and the small group sizes warrant a need for further studies to verify this in larger groups.
“The data is observational and we can’t be sure of cause and effect.
“Critically, if reproduced, we will need to understand whether possible impacts of maternal delivery and feeding on immune development or vaccine responses can be restored by, for example, manipulating the microbiome.”