There are several different types of immunity
During the first few months of our lives, we were all protected from infections by antibodies passed on to us by our mothers – in the uterus (via the placenta), and in breast milk. This type of immunity is known as passive immunity.
‘Big Picture: Immune System’
The antibodies last only a few months, though, so infants must quickly start developing their own long-lasting active immunity to protect them against different diseases. The thymus gland, where T cells mature, is most active just after birth and before puberty.
Before they are six months old, babies in the UK are immunised against diphtheria, tetanus, whooping cough, polio, rotavirus, meningitis C and other infections. The components of each vaccine encourage the immune system to develop its own defences against the disease. This is known as ‘artificial’ active immunity, whereas the kind of immunity that develops when the immune system comes into contact with the infectious agents of disease – often making you ill – is known as ‘natural’ active immunity.
Being immune to a disease means that you shouldn’t get ill with the same infection again. If a virus evolves, though, you can still catch the new strain.Lead image:
myllissa/Flickr CC BY NC ND