Before packing a vaccine carrier for a session, a health worker leaves frozen ice packs at room temperature until water begins to move inside them when shaken. Why is this conditioning step mandatory?
- A To increase the total cooling duration of the ice packs inside the carrier
- B To prevent freezing of freeze-sensitive vaccines such as hepatitis B and pentavalent placed next to the ice packs ✓
- C To allow the VVM on each vial to reset to its initial colour
- D To sterilize the outer surface of the ice packs before contact with vials
Correct answer: B. To prevent freezing of freeze-sensitive vaccines such as hepatitis B and pentavalent placed next to the ice packs
Explanation
Ice taken straight from the freezer sits well below zero and will freeze any adsorbed vaccine touching it, destroying potency. Conditioning lets the ice surface rise to around zero degrees so the carrier interior stays between 2 and 8 degrees Celsius. It shortens, not lengthens, effective cooling time, ruling out option A, and has nothing to do with VVM resetting.
Reference: Park's Textbook of Preventive and Social Medicine, 25th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.