The body acquires natural active immunity when it has been exposed to a pathogen and the immune system has destroyed the pathogen.B memory and T memory cells remain and will be activated if the pathogen is encountered in a subsequent infection.Antibodies typically stay in the blood for a few months to several years. Their lifespan depends on the specific disease and whether protection is from a past infection, a vaccine, or long-lived bone marrow cells.However, new born babies cannot make antibodies for the first couple of months.Some antibodies cross the placenta from mother to fetus, others are transferred to the baby in the mother's colostrum, the first milk the mother makes.
This gives the baby natural passive immunity that reflects the mother's active immunity for the first few months of life.
This gives the baby natural passive immunity that reflects the mother's active immunity for the first few months of life.