On the mechanics of chickenpox immunity for newborns and breastmilk antibody transfer

Question

According to my healthcare provider, a newborn should not be affected by chicken pox if it has immunity thanks to his mother having had the infection as a child herself - this immunity is apparently womb gained and lasts roughly a year. Let's assume that the infant is also breastfed exclusively - apparently, this assists the immunity because the mother's milk contains antibodies the newborn can use for resistance to various infections.

It seems like there is thus a mechanism where antibodies can be acquired from the mother and used by an infant to fight a disease. I'm told that breastfed babies do not get sick as often as formula fed ones, because disease the mother is exposed to causes antibodies to pass from the mother to the baby in the breast milk.

• is it true? I've only received this information anecdotally from midwives, but has it been subject to scientific scrutiny? Are the mechanisms well understood? (It seems unlikely to me that eating someone else's antibodies helps a person fight disease; why are the antibodies not digested and decomposed?)

• if true, does the newborn develop his own immunity from his own immune system, while it uses the mother's antibodies to fend off the chickenpox? Or does it replace his defence mechanism for a while (e.g the first year of life) to let him grow strong, but he will remain liable to contract illnesses like chickenpox later?

• if I, as an adult who has never had chickenpox myself, were to consume the breastmilk would I also benefit from enhanced resistance to chickenpox or other diseases the producer is exposed to/can generate antibodies for? Or is this antibody transfer mechanism limited to mother and child?

Answer 1

It is true that infants receive antibodies from the mother via the placenta in the final trimester of pregnancy and also in breastmilk.

Passive immunity

This is passive immunity, because the antibodies (usually IgA type) are passed on pre-formed. They can resist infection but do not form lasting immunity, which requires the body to encounter the infectious agent itself (specifically the antigens on its surface). After several weeks or months, the infant will become vulnerable again. It is important to note that the mother must have had the infection in question.

Antibodies in breast milk

This question on the Biology Stack Exchange asks about how antibodies in breastmilk survive digestion in the stomach of the infant. I refer to it’s answers. The structure of IgA antibodies and also the fact that the environment in the stomach of an infant is very different from that of an adult (specifically much less acidic so less protease activity). Their intestine is also more permeable. Thus adults would not derive the same benefit from breastmilk as infants do!

Chickenpox

You mention that you have never had chickenpox. This is a highly transmissible disease and hard to miss. Many adults who have never had chickenpox will actually have had subclinical infection (infection with no symptoms) and will have developed immunity. (Wallace et al.)

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Additional sources

Wallace MR, Chamberlin CJ,Zerbini L, et al. Reliability of a history of previous varicella infection in adults. JAMA 1997; 278:1520-1522.

NHS - How long do babies carry their mother’s immunity