Answer: Passive immunity
Step-by-step explanation:
The strategy of vaccination was a type of passive immunity. Passive immunity can be introduced artificially when antibodies are given as a medication to the non immune individual.
This is done in case of vaccination, attenuated form of bacteria is injected or orally given to the individual to evoke immune response when the body is exposed to the same bacteria again.
The attenuated form of bacteria evoke the immune system to produce memory cells which will kill the bacteria when it is encountered for the second time.