A district cold chain officer suspects that a shipment of pentavalent vaccine was accidentally frozen during transport. She performs the shake test comparing the suspect vial with a control vial that was deliberately frozen and thawed. The suspect vial shows sedimentation much faster than the control, forming a large sediment layer within 10 minutes. The correct action is:

• A Return the vials to the refrigerator and use them first at the next session
• B Shake vigorously again and use only if the sediment fully disperses
• C Send the vials back to the manufacturer for potency testing before use
• D Discard all suspect vials as they are damaged by freezing ✓

Explanation

The shake test identifies freeze damage in aluminium-adjuvanted vaccines such as pentavalent, DPT, Td and hepatitis B. Freezing causes irreversible clumping of the adjuvant, so the test vial sediments faster than the control and forms a distinct sediment layer. Such potency loss cannot be reversed by shaking, so all affected vials must be discarded. Potency testing is impractical at programme level and reuse risks giving ineffective antigen.

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.