Cocci - When can I put treated birds back in with flock?

I recently had a bout of coccidiosis here - I treated all the sick chicks in the house and medicated the healthy ones that were outdoors just in case, since they had a brief exposure to one of the older sick chicks.

Yesterday morning was the last dose of Sulmet and now everyone is getting water with ACV and a little bit of yogurt with their medicated feed to help repopulate their insides. Assuming they show no more symptoms, when will it be safe to put the chicks outdoors with the other birds?

I'm concerned that the ones outside that I treated never had it, therefore, wouldn't have built up an immunity to it? I don't want to infect them by putting the younger ones out too soon. I know they can carry it around in their systems for months and I won't be keeping them inside that long!

I appreciate everyone's help!

Leanne