Does breastfeeding help babies develop a strong immune system? If so, can breast milk protect a baby from COVID?


In addition to abundant and easily absorbed nutritional components, antioxidants and enzymes, breast milk helps to stimulate and strengthen a baby’s immune system and seemingly more now than ever, scientists have been looking at how breastfeeding may protect babies against infections, particularly COVID-19.  In fact, as of last week, the CDC changed their guidance for pregnant and lactating women and now strongly encourages women in both of those populations to get the COVID-19 vaccine to protect themselves and likely their babies as well.

Breast milk contains antibodies that can be passed from mother to baby throughout the duration of the time the mother continues to nurse and are even in the very first milk that a new mom makes, the colostrum. Not only does this allow the mom to pass on protection from infectious illnesses (colds, flu) that she has had in the past, but also those that occur while the baby is nursing. While it is not yet proven that nursing or pumping while having COVID (carefully with clean hands and a mask) or after can protect babies from COVID, several studies have found the antibodies that target the virus in human milk, so presumably the breastfed infant does get some protection. Similarly, recent studies also have demonstrated that COVID-19 mRNA vaccine antibodies get into breastmilk of lactating mothers and likely will confer protection. One theory is that the antibodies (likely IgA) work at the body’s entrance by coating the mouth, throat and gut of the baby preventing the virus from entering the body as easily. 

In addition to antibodies, breast milk also contains white blood cells that can be particularly helpful in helping to prevent gastrointestinal infections as well as building the immune system to appropriately respond to future infections. A recent study found that a specific type of white blood cells, called regulatory T cells, plays an important role in controlling the immune response to maternal cells transferred in maternal breastmilk and helps to decrease inflammation. There are also special proteins (lactoferrin and interleukins) that help balance the immune systems inflammatory response. Breastmilk also helps to develop the baby’s microbiome which plays a role in preventing infection. All of these things together help to decrease the risk of some chronic diseases including obesity, asthma and autoimmune diseases.

If you cannot breast feed or choose not to breast feed for personal or health reasons, fortunately some formulas now also have components to help with immune system development and you can always talk to your pediatrician about ways to support your baby’s current and future health.

Jacqueline Phillips, MD, August 17, 2021