Preformed antibodies are injected in such injury as pathogen i.e., Clostridium tetani produces a neurotoxintetanospasmin and a quick response is required to stop the action of antigen which is not done by the formation of our own antibodies as it takes time.
Weakened germs and dead germs are used in vaccine to develop immunity against them.
Wide spectrum antibiotics is used when a person is suffering from many diseases or infections but not for a single disease/infection