Before packing a vaccine carrier for an outreach session, the health worker leaves the frozen ice packs at ambient temperature until a film of water appears around them. Why is this conditioning step done?
- A To prevent freezing of freeze sensitive vaccines inside the carrier ✓
- B To increase the cold life of the vaccine carrier
- C To allow the VVM to equilibrate with ambient temperature
- D To reduce condensation that damages vaccine labels
Correct answer: A. To prevent freezing of freeze sensitive vaccines inside the carrier
Explanation
Ice packs straight from the deep freezer have surfaces well below zero degrees Celsius and can freeze vaccines they touch. Adsorbed vaccines such as DPT, TT, hepatitis A, pentavalent and PCV are irreversibly damaged by freezing. Conditioning at room temperature until the ice begins to move freely inside the pack raises the surface above zero degrees. It does not extend cold life; it protects against the opposite hazard, freezing.
Reference: WHO Immunization in Practice: A Practical Guide for Health Staff, 2015 update ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.