During a cold chain inspection, a supervisor suspects that a vial of DPT vaccine may have been frozen due to a malfunctioning ILR. Which test should be performed to confirm whether the vaccine has been damaged by freezing?
- A Vaccine Vial Monitor (VVM) reading
- B Shake test (freeze-damage test) ✓
- C Potency assay using ELISA
- D Visual inspection for discoloration only
Correct answer: B. Shake test (freeze-damage test)
Explanation
The shake test is the standard field method to detect freezing damage in aluminium-adjuvanted vaccines (DPT, TT, Hepatitis B, Pentavalent). A frozen control vial is kept alongside the test vial; after shaking, the test vial showing granular flaky sediment that settles slower than the uniformly suspended control indicates freeze damage. VVM measures cumulative heat exposure, not freeze damage. Freeze-damaged DPT must never be used as potency is lost irreversibly.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.