Why does our immune system save information about a infectious virus?
When an infectious pathogen the person's body launches a defense against the virus at the time that the immune system is fighting the virus, it also saves all the necessary information about the virus this specific action in the body is called primary response. So, next time the virus attacks the immune system is pre-equipped to deal with the attack, and hence inactivates the virus even before an infection is established and this is called secondary response.