## Comparison: IPV vs OPV ### Cold Chain Requirements **Key Point:** IPV and OPV differ fundamentally in their thermostability, which determines cold chain logistics and vaccine viability. | Feature | IPV | OPV | |---------|-----|-----| | **Vaccine type** | Inactivated (killed virus) | Live attenuated | | **Cold chain temperature** | 2–8°C (strict) | Can tolerate up to 37°C (heat-stable) | | **Thermostability** | Poor; degrades rapidly at room temperature | Excellent; remains potent even at higher ambient temperatures | | **Storage duration at room temp** | Hours only | Days to weeks | | **Mucosal immunity** | Weak/absent | Strong (IgA production) | | **Systemic immunity** | Strong (IgG) | Present but secondary | ### Clinical Significance **High-Yield:** OPV's superior heat stability made it the vaccine of choice for mass immunisation campaigns in resource-limited settings like India. This advantage is especially critical in areas with inadequate cold chain infrastructure. **Clinical Pearl:** India's switch from OPV to IPV in the routine schedule (while retaining OPV pulses for campaigns) reflects the balance between thermostability (OPV advantage) and safety (IPV advantage—no vaccine-derived poliovirus shedding). **Warning:** Do not confuse "heat-stable" with "no cold chain needed." OPV still requires proper storage; the point is it tolerates temporary excursions better than IPV. ### Why This Matters for NEET PG The cold chain is a cornerstone of vaccine delivery in India. Examiners test knowledge of which vaccines are thermolabile (IPV, measles, varicella) vs. thermostable (OPV, DPT, hepatitis B) because this directly impacts vaccination coverage in rural and remote areas.
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