Microbes that cause infectious disease are called pathogens.
Bacteria and Viruses reproduce rapidly inside the body. Bacteria often produce poisons/toxins that make us feel ill. Viruses live inside cells, causing damage; this also makes them harder to kill/treat without harming other cells.
White blood cells have two functions to defecnt against pathogens. Firstly, they produce anti bodies and anti toxins, which attatch to the bacteria or virus cell. Anti toxins counteract the toxins released by pathogens. Specific antibodies kill a particular pathogen. Secondly, they engulf and kill the pathogen.
Vaccinations are the insertion of a dead, or weakened (NOT reduced) pathogen into the body. The immune system then works against this, producing the anti bodies required to defend against the fully functioning pathogen. When the body encounters the real disease, the immune system recognises the pathogen and produces the required anti bodies, reducing the spread and reproduction of the pathogen.
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