The cold chain requirement for oral polio vaccine (OPV) is more stringent than for inactivated polio vaccine (IPV). OPV is stored at −15°C to −25°C in the cold chain. The key reason is:

• A OPV contains aluminium adjuvant that requires freezing to preserve adjuvant activity
• B IPV requires freezing because it contains formaldehyde-inactivated virus that is heat-stable
• C OPV contains VLPs (virus-like particles) that aggregate at room temperature
• D OPV is a live attenuated vaccine where thermal degradation kills the live viruses, abolishing vaccine efficacy ✓

Explanation

OPV is a live attenuated vaccine (Sabin vaccine) containing three serotypes of temperature-sensitive attenuated poliovirus; viability of the live virus is essential for efficacy. Heat rapidly inactivates the live virus strains, destroying vaccine potency. OPV must be stored at −15°C to −25°C (deep freeze) in the cold chain. IPV (Salk) contains killed (inactivated) virus, is heat-stable at 2–8°C, and can tolerate moderate temperature variations. The Vaccine Vial Monitor (VVM) on OPV vials detects cumulative heat exposure.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.