A cold chain assistant suspects that a carton of DPT vials was exposed to sub-zero temperatures during overnight transport. Which test confirms whether these adsorbed vaccine vials have been damaged by freezing?

• A Reading the vaccine vial monitor stage printed on the label
• B Shake test comparing the vial against a known unfrozen control vial of the same batch ✓
• C Checking the pH of the reconstituted suspension
• D Incubating one vial at 37 degrees Celsius and observing turbidity

Explanation

Freezing permanently aggregates the aluminium-adjuvanted antigen. In the shake test the suspect vial and a definitely unfrozen control vial from the same batch are shaken vigorously, then observed against light: the frozen vial shows rapid sedimentation of coarse granules while the control clears slowly. VVM measures cumulative heat exposure, not freezing, so option A cannot detect this damage.

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.