The Vaccine Vial Monitor (VVM) is a heat-sensitive label attached to vaccine vials. When should a vaccine vial be discarded based on VVM reading?

• A When the inner square turns lighter than the outer circle
• B When any color change occurs in the outer circle
• C When the VVM changes from white to light blue regardless of the square color
• D When the inner square becomes as dark as or darker than the outer circle ✓

Explanation

The VVM inner square turns progressively darker with cumulative heat exposure. The vaccine should be discarded when the inner square is as dark as or darker than the outer reference circle — this indicates the vaccine has been exposed to excessive heat and may no longer be potent. As long as the inner square is lighter than the outer circle, the vaccine can be used.

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.