In Estrus and Rabies shot

My 9 month old (today!!!) bitch came into heat on July 4th. We are waiting it out patiently and carefully, since we do not plan to spay her till she is older.

I set an appointment to have her first rabies shot on July 21. I am not sure if her heat cycle would be over by then.

So, my question is ... If she is still in heat, would it be OK to give her the rabies shot? Or do you suggest I wait till she is in the clear? And why?

Thanks.

~ Rei