But what of a newborn baby? It is not considered safe to vaccinate a newborn – their immune system is still developing, and vaccinating too early can cause the system to develop abnormally, and may even cause disease, depending on the type of vaccine used. So how can a baby be protected from disease in those first few months before vaccination?
The answer lies in passive immunity. Both during pregnancy and as a result of breast-feeding following birth, a baby can acquire passive immunity to infections its mother has been exposed to.
This occurs due to the presence of antibodies in the mother’s blood and breast milk. Antibodies present in blood can be transferred to the developing fetus across the placental barrier – and these can provide protection for a limited time after birth. More important is the protection provided to the baby after it has been born, in the form of antibodies which are present in the milk of its mother. Breastfeeding, therefore, is important for the health of the baby not only in terms of nutrition, but also in terms of providing protection from disease.
The type of immunity this provides is termed passive because it does not involve the baby developing its own immune response – the protection is derived not from the baby’s own immune system, but from that of its mother.