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Mothers May Give Infant Vaccines a Boost

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A mother breast feeding her baby.

Breast feeding increases the presence of a gut bacteria that may improve vaccine response in infants. (Photo by Jack Dykinga, K3095-10)

Breastfeeding Can Influence Development of the Infant Immune System

Mothers who breastfeed their infants regularly for the first 3 months of life can boost the infants’ response to vaccines, according to a recent multinational study.

That study, coauthored by Charles Stephensen, director of the Agricultural Research Service’s (ARS) Western Human Nutrition Research Center in Davis, CA, showed that breastfed infants in Bangladesh “responded robustly to vaccines, which provide protection against illness.”

Babies are born with a gastrointestinal (GI) tract that is essentially a blank slate from the microbiological standpoint, and breastfeeding promotes development of an intestinal microbial community that supports the development of the infant’s immune system. Stephensen explained that breast milk contains many components that can affect development of the immune system, including a specific type of carbohydrate (human milk oligosaccharides) that supports the growth of a bacteria called Bifidobacterium longum subspecies infantis (B. infantis) in the large intestine of human infants.

“This bacterium has many health benefits,” he said. “One is that it occupies space in the gut, keeping out some potential ‘bad actors’,” he said.

B. infantis also produces metabolites, including short chain fatty acids (SCFA) and other molecules, that help promote “regulatory” immunity. SCFAs help infants develop an immune system that prevents excessive inflammation and allowing the development of immunity to vaccinations.

“Our study showed that breastfed Bangladeshi infants with the highest percentage of B. infantis at 1-3 months of age had higher responses to vaccines given during that period, and that higher immune response persisted through 2 years of age,” Stephensen said. “This indicates that infants with higher B. infantis had better immune memory and thus likely had better protection against the infections targeted by such vaccines.”

In the United States, the vaccines traditionally given during a child’s first 4 months of life include hepatitis B, rotavirus, DTaP (diphtheria, tetanus, pertussis), Haemophilus influenzaea and pneumococcal conjugate (for bacterial pneumonia), and polio. They all stimulate an adaptive immune response that provides protection by producing antibodies and T-cells that specifically target those pathogens.

In addition to stimulating the development of infants’ immune systems, mother’s milk also helps infants fight off more run-of-the-mill ailments.

“Breastfeeding is healthier, in general, than feeding formula, when one thinks about immune protection,” Stephensen said. “Studies both internationally and in the U.S. have shown lower risk and better outcomes from common childhood infections – such as colds and GI infections that are commonly acquired by all infant and young children – in breastfed compared to formula-fed infants.”

Stephensen explained that the intestinal microbiome includes the total population of microorganisms – mostly bacteria – that inhabit the gut. Many of these are organisms, like bifidobacteria, that provide benefits to the infant. In adults, dietary fiber can serve a similar purpose to human milk oligosaccharides – feeding beneficial bacteria that provide health benefits in adults as B. infantis does in early infancy.

“I think we are just realizing how important appropriate development of the infant immune system is in protecting against infection and also protecting against over-reaction to common antigens that, in some circumstances, can result in autoimmune disease, food allergies, or asthma,” Stephensen said.

“The immune system must learn what to respond to in a protective manner, and what to leave alone,” he said. “Diet and the microbiome help the developing immune system respond appropriately, which sometimes means not over-responding. The infant’s developing immune system needs to get both parts right to control both infectious and, perhaps, decrease the risk of allergic diseases.”

Stephensen’s co-authors on the study were scientists from the University of California – Davis and the International Centre For Diarrhoeal Disease Research in Dhaka, Bangladesh. – By Scott Elliott, ARS Office of Communications

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