Surprise Reaction to Childhood Vaccines Linked to C-Section or Vaginal Birth

Children born via cesarean section may be at an immunological disadvantage compared to their natural birth peers, research suggests. A study, published in Nature Communications, found that the birth delivery method can affect how a child's immune system responds to certain vaccinations, with natural births resulting in a significantly higher immune response than those born via c-section.

The reason for these differences appears to be caused by the infants' microbiomes.

Your body is home to trillions of microorganisms, collectively known as your microbiome. The motherload of these microbes is found in your gut and has been implicated in everything from digestion to depression. They also play a vital role in supporting your immune system.

child receiving vaccine
Stock image of an infant receiving a vaccine. The birth delivery method can affect how a child's immune system responds to vaccination. Getty/dimamorgan12

Professor Debby Bogaert of the Centre for Inflammation Research at the University of Edinburgh, who led the study, told Newsweek: "The microbiome, including the identified bacteria associated with improved vaccine responses in our study, have been shown to support maturation and function of the immune system, and thereby support the immune system to respond to infections."

The researchers examined 101 newborns and assessed their intestinal microbiomes throughout their first year of life. They found that babies born via vaginal delivery had significantly higher levels of E. coli and Bifidobacterium bacteria in their guts—the key component of many probiotic supplements. Those babies showed higher antibody levels in response to vaccination.

"Our research suggests that c-section-born babies mount less strong responses to the studied vaccines compared to naturally born babies," Bogaert said. "We identified several beneficial microbes to be the link between mode of delivery and vaccine response."

Whether these elevated antibody levels actually correspond to increased immune protection is yet to be determined. The study only looked at two routine childhood vaccinations, against pneumococcal lung infection and meningitis.

Although some women do choose to undergo a c-section, the procedure is often done as an emergency operation for the safety of the mother and child. There is also evidence that the microbiomes of c-section babies do eventually catch up to those of their naturally born peers.

Woman holds hands around healthy gut
Stock image illustrating a healthy gut. The gut microbiome is involved in everything from digestion to depression. Meeko Media/Getty

"The composition of the microbiome in c-section-born babies indeed catches up in the months following birth," Bogaert said. "However, we know that especially the first weeks to months in life are essential for immune system maturation in life.

"In the future, we may be able to supplement those bacteria to children born by c-section shortly after birth."

Breastfeeding has also been shown to have a significant impact on a child's microbiome. "We found that infants born by natural delivery and subsequently breastfed had increased levels of microbes that were related with higher vaccine responses."

As we age, our gut microbiomes continue to play an important role in regulating our immune response, but lifestyle factors like diet and medication become more important determinants of our microbial composition.

"There are ample studies showing evidence that the microbiome of the gut affects the immune responses in adult life," Bogaert said. "However, [largely] due to differences in diet, other microbes might additionally be at play in older children and adults, compared to infants.

"To understand this better, this would require new studies," Bogaert said.

Do you have a tip on a science story that Newsweek should be covering? Do you have a question about vaccines? Let us know via


de Koff, E.M., van Baarle, D., van Houten, M.A. et al. Mode of delivery modulates the intestinal microbiota and impacts the response to vaccination. Nat Commun. November 15, 2022,