An auxiliary nurse midwife returns from a session site where her vaccine carrier accidentally sat inside a freezer overnight, containing several vials of DTwP-HepB-Hib pentavalent vaccine. She performs the shake test on a suspect vial: on tilting, sediment settles rapidly within minutes leaving a clear supernatant. What is the correct action?

• A Use the vials immediately since potency loss from freezing is minimal
• B Warm the vials to room temperature for 24 hours and then retest before deciding
• C Return the vials to the freezer and use them within one week
• D Discard all suspect vials as they have been damaged by freezing ✓

Explanation

Pentavalent, DTP, TT/Td and hepatitis D are adsorbed aluminium-based vaccines that are freeze sensitive. Freezing causes irreversible clumping of the adsorbed antigen; the positive shake test shows rapid sedimentation with a clear supernatant layer, confirming freeze damage. Such vials have altered potency and increased local reactogenicity, so all suspect vials from that batch exposure must be discarded. Warming cannot reverse clumping, and retesting a known positive result wastes doses.

Reference: WHO Manual on the Management of Cold Chain and Immunization Operations, 2015 ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.