Question

what are vaccine how they produce immunity

Answer 1

A vaccine is a biological preparation that provides active acquired immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism and is often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins.

Answer 2

Vaccine is a biological preparation which provides active acquired immunity to a particular disease.
They are like a training course fir the immune system which makes them strong to fight the particular disease. During vaccine small group of the pathogens of the disease which are weakened is injected in the body, for making the body understand what it is and counter it .
So if some strong and great amount of pathogens of the disease enter the body .
The immune system is ready to fight.