Active and passive immunity
At the doctor’s you can get immunised against pathogens with a vaccine.
There are two ways to get immune.
A vaccine contains dead or inactive pathogens. These pathogens still have antigens on their surface, so that the immune-reaction of station 5 still works. You get immune but won’t get ill, as the pathogens are dead. Sometimes you have to get vaccinated two or three times to make the body react to the antigens again. Every time of vaccination the number of memory cells get higher and the reaction to the real/living pathogen will be faster.
With passive immunity you don’t get infected with the real pathogen. The doctor injects antibodies against the pathogens itself. This is only used if the infection has happened and the doctor wants to give the body a rapid/fast protection against the pathogen.