The oral polio vaccine (bOPV — bivalent types 1 and 3) is stored at −15 to −25°C in the cold chain. During a health camp, power failure occurs for 20 hours; the vaccine container has a vial monitor (VVM) that shows the inner square darker than the outer circle. What action should be taken?

• A Use the vaccine immediately — VVM change is irreversible but does not affect potency
• B Keep the vaccine for 2 more days at 2–8°C and recheck VVM
• C Use within the same session only as partial potency remains
• D Discard the vaccine — VVM indicates cumulative heat exposure has exceeded safe threshold ✓

Explanation

The Vaccine Vial Monitor (VVM) is a heat-sensitive label that undergoes irreversible colour change with cumulative heat exposure above the acceptable threshold. When the inner square matches or becomes darker than the outer circle, the VVM has reached stage 3 or 4, indicating that the vaccine should not be used and must be discarded because the cold chain integrity has been irreparably compromised. The open vial policy permits multi-dose vials to be used across sessions at 2–8°C for up to 4 weeks under specific conditions, but only if the VVM has not reached discard point. A darkened inner square overrides all other considerations.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.