Good afternoon and thank you for your warm welcome, this will be the first talk in a series of five on Health interventions, protection and prevention. Could I start by asking for a show of hands, how many of you had a flu vaccination at the beginning of winter？I thought so. You young ones always think you're indestructible. Well, as you are no doubt aware disease-spreading germs or pathogens are everywhere, on a daily basis the human body has to ward off attacks by various harmful bacteria and viruses, a healthy body has a good defense system against many of these germs but the defense only operates well against micro-organisms that it has already encountered, in which case it is said to be immune. There are two ways in which humans acquire natural immunity, actively, when a person has first suffered and then recovered from an illness, and passively, when ready made protection is transferred into the body, for example, from the maternal blood via the umbilical cord to an unborn child, or through breast milk. Now, artificially acquired immunity can help the body to fight disease, so we can use active immunization as a preventative measure. This is when a person is vaccinated against an illness by injection or oral ingestion of a tiny amount of weakened or inactive germs, not enough to actually cause him or her to contract the illness but sufficient for the body's defense system to recognize and respond to the threat by forming antibodies.
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