How did the time it took the body to respond to the pathogen change after the second exposure?

When a foreign antigen or pathogen enters our body, our immune cells detect it and generate a response by producing antibodies against it. Also, our immune cells generate memory cells so that our body remembers this pathogen if it invades the body afterwards. Hence, it takes less time for an organism's body to generate a response when a pathogen invades for the second time. The memory cells immediately detect the pathogen and a response is generated.

"it built up in the atmosphere"

i think thats it, idk, i tried looking for this exact q& a for grad. and idk if i got this question right or sorry if im wrong