Why do some people get chlamydia and others don't?

More than you think: Chlamydia is an std caused by a tiny bacteria-like critter that lives inside of cells. There are often very few symptoms with chlamydia so folks can have it and not know it. It can have very dramatic symptoms as well, such as pid (which can be very serious!). Condoms can provide some protection but abstinence till you are with one person forever is the only truly safe bet for prevention.

STD risk: Lower risk by using condoms....Have partners checked....Sometimes just bad luck....