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**Drug:** Attenuated Vaccines (e.g., MMR, Varicella, Rotavirus, Live Influenza)
## Overview
Attenuated vaccines contain live, weakened forms of viruses or bacteria that replicate in the body, inducing a strong and long-lasting immune response without causing significant illness in immunocompetent individuals.
## Primary Indications
* **MMR (Measles, Mumps, Rubella):** Prevention of measles, mumps, and rubella.
* **Varicella:** Prevention of chickenpox.
* **Rotavirus:** Prevention of rotavirus gastroenteritis.
* **Live Influenza Vaccine (LAIV):** Prevention of influenza.
* **BCG (Bacillus Calmette-Guérin):** Prevention of severe forms of tuberculosis in infants and children in endemic areas.
## Adult Dosing
* **MMR:** 0.5 mL IM or SC, 1 or 2 doses depending on vaccination history and need for a booster.
* **Varicella:** 0.5 mL SC, 2 doses separated by 4-8 weeks.
* **LAIV:** 0.2 mL (0.1 mL per nostril) intranasally, annually.
* **BCG:** Dosing varies by formulation and country; typically administered intradermally.
## Pediatric Dosing
* **MMR:**
* 1st dose: 0.5 mL IM or SC at 12-15 months of age.
* 2nd dose: 0.5 mL IM or SC at 4-6 years of age.
* **Varicella:**
* 1st dose: 0.5 mL SC at 12-15 months of age.
* 2nd dose: 0.5 mL SC at 4-6 years of age.
* **Rotavirus:** Oral vaccine. Dosing and schedule depend on the specific product (e.g., 2 mL, 2.5 mL, or 5 mL per dose, given at 2, 4, and sometimes 6 months of age).
* **LAIV:**
* Children 2 years and older: 0.2 mL (0.1 mL per nostril) intranasally, annually.
* **BCG:** 0.05 mL or 0.1 mL intradermally, typically at birth or shortly after, depending on country guidelines.
## Dose Adjustments
Dose adjustments are not typically required based on renal or hepatic impairment for standard attenuated vaccines in immunocompetent individuals. However, contraindications related to immune status are paramount.
## Contraindications
* **Severe, life-threatening allergic reaction (anaphylaxis) to a previous dose of the vaccine or to any component of the vaccine, including neomycin and gelatin (for varicella and MMR).**
* **Primary and secondary immunodeficiency states:** Includes congenital immunodeficiency, AIDS, treatment with immunosuppressive drugs (e.g., high-dose corticosteroids, chemotherapy, radiation therapy), and certain leukemias or lymphomas.
* **Pregnancy:** Live virus vaccines are generally contraindicated in pregnant women due to a theoretical risk to the fetus. Vaccination should be deferred until after pregnancy.
## Adverse Effects
* **Common:** Mild fever, rash, transient lymphadenopathy. Local injection site reactions (pain, redness, swelling) for injectable vaccines.
* **Less Common/Rare:** Febrile seizures (associated with fever), thrombocytopenia (temporary), Guillain-Barré syndrome (very rare association). Severe allergic reactions are rare.
## Key Drug Interactions
* **Immunosuppressive agents:** Concurrent administration may reduce the immunogenicity of live attenuated vaccines. Vaccination should ideally be completed at least 2 weeks before initiating immunosuppressive therapy, or delayed until the therapy is discontinued and immune function has recovered.
* **Antibodies (e.g., immunoglobulin, blood products):** The presence of passively acquired antibodies can interfere with the replication of live attenuated viruses and reduce vaccine efficacy. Vaccine administration should be separated from administration of antibody-containing products by specific time intervals, which vary depending on the product and vaccine.
## Monitoring
* Monitor for signs of allergic reaction immediately following vaccination.
* Educate patients and caregivers on common side effects and when to seek medical attention.
* For individuals on immunosuppressive therapy, assess immune status before and after vaccination.
## Clinical Pearls
* Attenuated vaccines provide robust, long-lasting immunity and are generally preferred when available and appropriate.
* Live attenuated vaccines are contraindicated in pregnant women. Advise on contraception for at least 1 month after vaccination with MMR or varicella.
* Vaccination providers must be aware of the specific contraindications and precautions for each live attenuated vaccine, especially regarding immune status.
* LAIV is generally preferred over inactivated influenza vaccine for children aged 2-17 years, unless contraindicated.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and local guidelines before administering any medication. Dosing and indications can vary based on individual patient factors, specific product formulations, and evolving clinical guidelines.
