A Vaccine Vial Monitor (VVM) is attached to vaccine vials to indicate heat exposure. The VVM reaches the discard point when:
- A The inner square becomes the same colour or darker than the outer circle ✓
- B The inner square becomes lighter than the outer circle
- C Any colour change is seen in the outer circle
- D The inner square changes from white to blue
Correct answer: A. The inner square becomes the same colour or darker than the outer circle
Explanation
A VVM is a heat-sensitive label where the inner square progressively darkens with cumulative heat exposure. The discard point is reached when the inner square matches or is darker than the outer reference circle — at this stage the vaccine should not be used. When the inner square is lighter than the outer circle, the vaccine is still usable (provided other criteria are met). Colour change to blue or white is not how VVMs function.
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.