Final answer:
A vial that should be used immediately after opening and has no preservatives is known as a single dose vial, which is intended for one-time use only to prevent contamination.
Step-by-step explanation:
A vial that does not have any preservatives and thus requiring it to be used immediately after opening is known as a single dose vial. This type of vial is specifically designed to be used once and then discarded to prevent the risk of contamination and infection.
Unlike multiple dose vials, which contain preservatives that allow them to be used for more than one dose, single dose vials do not contain these preservatives, making them suitable only for a single use.