I took tetanus injection nearly 10 days ago from a medical shop. Then constantly I am thinking that the boy used a new syringe or not. I have seen him to remove the cap and air inside the syringe. But I did not notice  whether he took the syringe from a plastic wrapper or not. I asked him personally after that, he has assured me more than once that they always use new syringe. Don't know constantly this doubt is running at my mind. Last 10 days constantly I am thinking about this and feeling very much anxious and helpless.