A Vaccine Vial Monitor (VVM) shows a colour change where the inner square is darker than the outer ring. The correct action by a vaccintor is:
- A Use the vaccine immediately as the VVM shows optimal storage
- B Use the vaccine if the expiry date is valid and store at −20°C
- C Do not use the vaccine — the heat threshold has been exceeded ✓
- D Check the freeze indicator before deciding to use the vaccine
Correct answer: C. Do not use the vaccine — the heat threshold has been exceeded
Explanation
The VVM endpoint is reached when the inner square becomes the SAME colour as or DARKER than the outer ring — this indicates cumulative heat exposure has exceeded the safe threshold and the vaccine should NOT be used regardless of expiry date. When the inner square is still lighter than the outer ring, the vaccine can be used. The VVM tracks heat exposure only; the shake test and freeze indicator are used to detect freeze damage to freeze-sensitive vaccines like DPT, Hepatitis B, and liquid pentavalent.
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.