## Live Attenuated Vaccines **Key Point:** Live attenuated vaccines contain weakened (attenuated) forms of the pathogen that can replicate in the host but cause minimal or no disease while generating robust immune responses. ### Characteristics of Live Attenuated Vaccines - Contain viable but weakened microorganisms - Replicate in the host, mimicking natural infection - Induce both cellular and humoral immunity - Provide long-lasting, often lifelong immunity - Require careful cold chain maintenance (typically 2–8°C) - Contraindicated in severely immunocompromised individuals ### Common Live Attenuated Vaccines in India | Vaccine | Type | Route | | --- | --- | --- | | MMR (Measles, Mumps, Rubella) | Live attenuated | Subcutaneous | | Varicella | Live attenuated | Subcutaneous | | Rotavirus (RotaTeq, Rotavac) | Live attenuated | Oral | | Yellow Fever | Live attenuated | Subcutaneous | | OPV (Oral Polio Vaccine) | Live attenuated | Oral | **High-Yield:** MMR is the classic live attenuated vaccine tested in NEET PG. It is given at 9–12 months and 15–18 months in the Indian immunisation schedule. **Clinical Pearl:** Live attenuated vaccines should not be given within 4 weeks of each other if administered on different days, as the immune response to the first vaccine may interfere with the second. **Mnemonic: LAVA** — Live Attenuated Vaccines Attenuate (weakened pathogens that replicate).
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