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# Attenuated Vaccines ## Overview Attenuated vaccines contain live, weakened (attenuated) microorganisms that do not cause disease in individuals with healthy immune systems but do elicit an immune response. ## Primary Indications Prevention of specific infectious diseases, including but not limited to measles, mumps, rubella, varicella, rotavirus, oral polio, and yellow fever. ## Adult Dosing Dosing is specific to the individual vaccine and formulation. Refer to the manufacturer's product information for each specific attenuated vaccine. ## Pediatric Dosing Dosing is specific to the individual vaccine and age/weight recommendations. Refer to the manufacturer's product information and current immunization schedules (e.g., CDC) for specific pediatric dosing. ## Dose Adjustments No dose adjustments are typically made. Vaccination is generally given as a single dose or a series of doses according to recommended schedules. ## Contraindications * **Severe immunocompromise:** Including but not limited to congenital immunodeficiency, advanced HIV infection (e.g., CD4 count <200 cells/mm³ in adults), solid organ or hematopoietic stem cell transplant recipients on immunosuppressive therapy, and patients receiving high-dose corticosteroids or other potent immunosuppressive agents. * **Pregnancy:** For certain vaccines (e.g., MMR, varicella). * **History of anaphylactic reaction:** To a previous dose of the vaccine or any of its components. * **Specific contraindications for individual vaccines:** For example, certain oral vaccines (e.g., rotavirus) are contraindicated in infants with a history of intussusception. ## Adverse Effects Common: Fever, rash, injection site reactions (pain, redness, swelling). Less Common/Rare: Thrombocytopenia, febrile seizures, encephalitis (very rare), Guillain-Barré syndrome (rare association with some vaccines). Anaphylaxis is a rare but serious adverse event. ## Key Drug Interactions * **Immunosuppressive medications:** Can reduce the efficacy of attenuated vaccines and increase the risk of disseminated infection. Defer vaccination until immunosuppressive therapy is discontinued or significantly reduced. * **Other live vaccines:** Concurrent administration may be possible, but specific recommendations exist regarding spacing or using the same syringe for certain combinations (e.g., MMR and varicella). Refer to immunization guidelines. * **Antibiotics:** Certain antibiotics may affect the viability of some oral attenuated vaccines (e.g., oral polio, rotavirus). ## Monitoring * Monitor for expected post-vaccination reactions (fever, rash). * Educate patients/caregivers on signs/symptoms of serious adverse events and when to seek medical attention. * Document vaccination date, vaccine product, lot number, and administration site. ## Clinical Pearls * Attenuated vaccines provide robust and long-lasting immunity. * Contraindications are primarily related to severe immune deficiency and pregnancy. * Always consult current immunization schedules and manufacturer package inserts for the most up-to-date recommendations on administration, contraindications, and precautions. *** **Disclaimer:** This information is intended for healthcare professionals. Always verify current prescribing information and consult relevant guidelines before making clinical decisions.