A cold chain worker notices that the vaccine vial monitor (VVM) on an OPV vial shows the inner square darker than the outer circle. What should the health worker do?

• A Use the vaccine immediately as VVM change indicates potency is preserved
• B Shake the vial and use if no clumping is observed
• C Return the vial to the refrigerator and recheck after 24 hours
• D Discard the vaccine as the VVM indicates heat damage beyond acceptable limit ✓

Explanation

A VVM reading where the inner square is darker than or matches the outer circle indicates that the vaccine has been exposed to excessive heat and should be discarded. VVM Stage 3 (inner square same colour as outer circle) and Stage 4 (inner square darker) both signal discard. Only VVMs in Stage 1 or 2 (inner square lighter than outer circle) indicate the vaccine is still usable.

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.