A vaccine vial monitor (VVM) on a tetanus toxoid (TT) vial shows the inner square is the same colour as the outer circle. At which VVM stage is this, and what is the correct action?

• A Stage 1; the vial is safe to use
• B Stage 4; the vial must be discarded
• C Stage 3; the vial must be discarded
• D Stage 2; the vial is safe to use ✓

Explanation

VVM Stage 2 is when the inner square matches the outer circle in colour. The vial is still usable at this stage. Stage 3 is when the inner square is darker than the outer circle, meaning discard. Stage 4 is when the inner square is much darker. Stage 1 is when the inner square is lighter than the outer circle, indicating minimal heat exposure.

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.