Edward Jenner ( ) – father of vaccination, developed a vaccine for smallpox

 Vaccine consists of dead or weakened bacteria or viruses, or modified bacterial poisons  The organism or poison act as an antigen, but because it is modified or weakened, it can no longer cause disease  When vaccine is injected into the body, the immune system responds to it as it would be the pathogen and produces antibodies or killer T cells  So, immunity is gained without suffering through the disease

Benefits  Total elimination of diseases  Prevention of epidemics & pandemics  Decreased health-care costs  Prevention harmful side-effects of diseases Risks  Possible toxic effects of chemicals such as mercury in vaccines  Possible overload of the immune system  Possible links with autism