Chickens do sneeze, but what you want to watch for is wet, snotty sneezing, wet coughs, runny or foamy eyes, wheezing or rattling in the chest. And they don't generally carry on like that for several months. They get sick and either get over it or die. So I'm not sure what would be going on with your bird. Many poultry respiratory diseases are indeed viral but what usually kills the bird is the pneumonia and secondary bacterial infections that set in very quickly. That's why antibiotic's are needed in most cases.
All you can do is try and see what works. If you've wormed them and you want to give them a round of antibiotic's after a few days then go ahead and see if you get any improvement.
All you can do is try and see what works. If you've wormed them and you want to give them a round of antibiotic's after a few days then go ahead and see if you get any improvement.