The first thing you need to do is to inform the screen reader that you are in a modal. This can be done either by replacing the div with the dialog element, or by giving the div a role attribute: role="dialog". If you then open the dialog, you will have the opportunity to read the contents of the modal, as the screen reader knows what is part of the open content. Additionally, if you add aria-labelledby="modal-header", the screen reader will read the label before starting to read the input field. You can also use aria-describedby if there is some kind of introduction in the modal.