The Vaccine Vial Monitor (VVM) changes color from light to dark when exposed to cumulative heat. A vial is discarded when:

• A The inner square is darker than the outer circle ✓
• B The inner square matches the color of the outer circle
• C The inner square is lighter than the outer circle
• D Any color change is noted in the inner square

Explanation

The VVM consists of an inner square within an outer circle. The VVM changes progressively from light to dark as cumulative heat exposure increases. The rule is: DO NOT USE when the inner square is the same color as or darker than the outer circle. If the inner square is lighter than the outer circle, the vaccine is usable. The VVM is placed on the vial cap and serves as a heat exposure indicator; it does not monitor for freezing.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.