James was exposed to a pathogen when he was 10 years old and felt ill.

what would most likely happen if he were exposed to the same pathogen when he is 12 years old?

His body would most likely not become entirely immune to the same pathogen, but there are at least two outcomes that could occur, he can become more susceptible to getting the pathogen again, now that it has already affected his body once, or his body would be more equipped to protect itself against the pathogen.

thinking it would be physical characteristics