by giving vaccine it means we inject the same infection causing organism in our body in a very benign form , so that our body can built immunity and develop resistance for future to prevent the severe form of the disease in developing in our children. But somr times the vaccines can cause minor symtoms in our body for which we need to give treatment like pcm for fever and anti allergic for rashes. In your childs case it seems to be a minor illness which is caused by the vaccine