Potency

Part of our immune system is passed on to us as newborns from our mothers through the placenta during our time spent in the womb, and again through feeding on breast milk. Immunity to particular viruses and bacteria and the potency of this passive immunity differs from mother to mother. For example, mothers who have had chickenpox during their lifetime can pass on that immunity to their newborn. However, this form of passive protection is short-lived and begins to decrease after the first few months of life. Over time, the immune system acquires more complex immunities after reacting with pathogens from the outside world.