## Live Attenuated Vaccines and Cold Chain Requirements **Key Point:** Live attenuated vaccines are temperature-sensitive and require strict cold chain maintenance at 2–8°C. Once reconstituted, they have a short shelf life (often 4–6 hours) and must be discarded if not used promptly. **High-Yield:** MMR is the classic example of a live attenuated vaccine with stringent cold chain requirements. It is supplied as a lyophilized (freeze-dried) powder that must be reconstituted with sterile diluent immediately before use. ### Cold Chain Sensitivity | Vaccine Type | Storage Temperature | Reconstituted Shelf Life | Example | |---|---|---|---| | Live attenuated | 2–8°C (refrigerated) | 4–6 hours (discard if unused) | MMR, Varicella, OPV | | Inactivated | 2–8°C | Stable as supplied | IPV, DPT, Hepatitis B | | Toxoid | 2–8°C | Stable as supplied | Tetanus, Diphtheria | **Clinical Pearl:** Freeze-thaw cycles damage live attenuated vaccines irreversibly. Cold chain monitoring (use of vaccine vial monitors and temperature logs) is mandatory in immunization programs to prevent wastage and ensure efficacy. **Mnemonic:** **LOVE** — **L**ive attenuated vaccines are **O**ften **V**ery **E**xpensive and temperature-sensitive.
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