Tapeworms are pretty benign, as far as worms go, but if the dog has a lot of them they can cause anemia. Dogs
that have
tapeworms do sometimes have other worms
that cause more severe sickness, so if you see tapeworms, then you will want to do a fecal check for other species of worms, too. Hopefully that was done when you went to the vet two weeks ago, so the doctor can decide whether you need to repeat the worming for other species or just for the tapeworms.