The cold chain requires that oral polio vaccine (OPV) be stored at which temperature, and what is the vaccine vial monitor (VVM) used for?
- A OPV stored at 2°C to 8°C like most vaccines; VVM indicates freeze damage
- B OPV stored at −40°C to −80°C (ultra-cold); VVM monitors moisture exposure
- C OPV stored at −15°C to −25°C; VVM is a heat-sensitive label on the vial that changes colour irreversibly if the vaccine is exposed to excessive heat, indicating it should not be used ✓
- D OPV stored at room temperature; VVM monitors UV light exposure
Correct answer: C. OPV stored at −15°C to −25°C; VVM is a heat-sensitive label on the vial that changes colour irreversibly if the vaccine is exposed to excessive heat, indicating it should not be used
Explanation
OPV is the most heat-sensitive vaccine in the national immunization schedule and must be stored frozen at −15°C to −25°C (or −20°C). The vaccine vial monitor (VVM) is a thermochromic label attached to each vial; it contains a heat-sensitive polymer whose inner square darkens irreversibly with cumulative heat exposure — when the inner square matches or is darker than the outer ring, the vaccine has exceeded its heat budget and must be discarded. VVM is specifically a heat exposure indicator, not a freeze or moisture indicator.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.