[Sally Le Page (OP)]

This week listener Rick emailed us to ask:

"Why do we acquire lifelong immunity against some pathogens but not others?"

We got infectious disease researcher John Tregoning to give us his answer, which you can listen to here: https://www.thenakedscientists.com/podcasts/question-week/why-do-we-keep-catching-same-diseases [nofollow]

[Liaata]

I think this has something to do with our immune system. It can learn to defend some bacteria and viruses, but not all of them. After some time the immune system forgets what the attackers looked like and some diseases evolve by time as well.

[alancalverd]

Because pathogens do not negotiate.