What effect does the vaccine have on the body?

Answer 1

A vaccine contains the pathogen ( a foreign body which causes diseases/illnesses) which the virus is designed to provide protection for ie: a flu vaccine will contain a flu virus, measles has the measles virus etc... - but they have been treated so they are in effect dead and so will cause no symptoms, your body can only recognise a pathogen, it does not know that it is dead and can not harm you,so your body produces antibodies ( cells that fight off and remove pathogens from the body) to fight this vaccine, the antibodies remain in the body forever (unless you have an autoimmune/immunodeficiency illness) so when you come into contact with say the flu your body already has the antibodies and you don't get sick because your body removes the pathogen before it gets chance to take hold.