Strep throat is definitely not a little kid illness. You can get it ANY time at ANY age.
You're lucky you got the shot, it takes like 24 hours to feel better, SO fast! When untreated strep infections can go to your heart and can be fatal. No joke. Luckily, you're now protected by the shot.
I've had it TONS and always ask for the shot because it's quicker.
Get well soon