But really, how many can you need? Well... in 5 injections I'm now covered for Hep A, Hep B, Diptheria, Tetanus, Polio, Typhoid and against some other random and unpleasant sounding illnesses that I never heard about until now. I'm riddled with tiny amounts of the lot so my immune system can do some very clever shit and make me all strong and that. I'm basically iron man... well kind of... I might still get run over by a bus.