Why do some people consistently get strep while others never get it?

[Anonymous]

I was supposed to have my tonsils out as a teen, but my parents were too distracted by my younger brother to get around to my having the surgery.
When I get strep, it's never just strep throat. I get double ear infections, a sinus infection, and double conjunctivitis at the same time. The first time it happened, I thought I was just unlucky. The second time, I started getting nervous. Now, it's an annual event. My PCP can't explain it. She said that she doesn't recommend having my tonsils out at this point because the risk of complications outweighs the potential benefits.