A VVM on a TT (tetanus toxoid) vial is at Stage 3 (inner square darker than outer circle). The vial was stored correctly at +2 to +8°C throughout. What is the correct action?

• A Use the vial only if it has been opened within the last 4 weeks
• B Return it to the district cold chain point for re-testing
• C Continue using it because TT is heat-stable and the VVM can be ignored
• D Discard the vial immediately regardless of expiry date ✓

Explanation

When the VVM inner square becomes darker than the outer circle (Stage 3), the vaccine has exceeded the discard point and must be discarded regardless of expiry date or storage conditions. TT is freeze-sensitive but heat-labile; the VVM cannot be ignored. Option A is wrong because an opened vial with a spent VVM is not usable. Option C is wrong because TT is not heat-stable enough to ignore VVM Stage 3. Option B has no cold chain protocol.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

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Written and medically reviewed by the StethoPrep medical team.