you need a vent on the shower drain also. it can be tied back into the vent from the lav at 42 inches above the floor or higher. if you tie into the lav vent make sure the tee is upside down from the one the lav drains into.
in all the states i have worked that would not pass inspection. now if you tee off of the line going to the shower for the lav that would work. im not saying what you have wouldn't work, it just wouldn't pass inspection where i have been.