The picture is oriented vertically for me... I assume that the small berries are the store blueberries. The large berries at the top don't necessarily strike me straight away as a vaccinium. Could you take a closeup of one Berry in better light? One from both sides of the berry. You didn't happen to take a picture of the plants themselves, did you?

What did the berries in question taste like, since you ate them?

Well, I find blue berries to be really sweet normally. These were like "half sweet" blueberries almost. They were lacking some sweetness I think, but definitely not completely bitter tasting. Attached is the same photo but a closeup. The small berries are the wild ones, the big ones were the store bought. All the below berries are wild berries. In the first picture, the larger ones were store bought.

They certainly are consistent with blueberries, but having photos (close-up and the whole plant) of the bush they were picked from with something for scale would help confirm.

Hmm, unfortunately no berry bush pictures. :( Thanks a lot for the input. I only have frozen bags of these. Since they made me sick anyway, I won't plan on eating them.

Yeah, those sure look just like vaccinium to me and, as GG mentioned, there are no poisonous members. At this point we would need a leaf picture to tell any more. Could it be that you didn't eat any other berries that looked similar and you only showed us the vaccinium? Or that you had food poisoning from something else that day and misattributed it?