The Vaccine Vial Monitor (VVM) changes from a lighter to a darker colour based on cumulative exposure to:
- A Freezing temperatures
- B Heat exposure over time ✓
- C Light exposure (photodegradation)
- D Mechanical shock and vibration
Correct answer: B. Heat exposure over time
Explanation
A Vaccine Vial Monitor (VVM) is a heat-sensitive indicator that changes colour (inner square darkens relative to outer circle) based on cumulative heat exposure over time, following an Arrhenius reaction. It is NOT sensitive to freezing temperatures — freeze-sensitive vaccines (DPT, hepatitis B, IPV, Td, TT) can be damaged by freezing without any VVM change. The shake test is used to detect freeze damage.
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.