I just switched over to Depo Provera from Alesse 28. When I got the shot, I was on my 8th week in a row of active pills (I was skipping periods using pills). I stopped taking my pills the day after I got my shot (I got the shot on a Tuesday, I took my Tuesday pill that day as well, but didn't take any more after).

Will the Depo shot be effective right away because I was on another form of contraception when I got the shot? Or how long should I wait before having unprotected sex?