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# Attenuated Vaccines
## Overview
Attenuated vaccines are live vaccines that contain weakened (attenuated) forms of viruses or bacteria. They stimulate an immune response similar to natural infection without causing significant illness.
## Primary Indications
Prevention of infectious diseases, including measles, mumps, rubella, varicella, rotavirus, oral polio, yellow fever, and BCG.
## Adult Dosing
Dosing varies significantly by vaccine and manufacturer. Consult specific vaccine product information. Generally, a single dose is administered, although some vaccines may require a second dose for optimal immunity.
## Pediatric Dosing
Pediatric dosing is vaccine-specific and age-dependent. Schedules are established by national immunization guidelines (e.g., CDC in the US). Common examples include:
* **MMR (Measles, Mumps, Rubella):** Typically given at 12-15 months and again at 4-6 years.
* **Varicella (Chickenpox):** Typically given at 12-15 months and again at 4-6 years.
* **Rotavirus:** Oral administration, typically a series of 2 or 3 doses starting at 2 months of age.
## Dose Adjustments
Dose adjustments are generally not applicable as these are vaccines. However, contraindications and precautions may preclude administration.
## Contraindications
* **Severe immunodeficiency:** Including congenital immunodeficiency, symptomatic HIV infection, prolonged high-dose corticosteroid therapy, chemotherapy, or radiation therapy.
* **Pregnancy:** Live attenuated vaccines are generally contraindicated in pregnancy. Pregnancy should be avoided for at least 1 month after vaccination with certain live vaccines (e.g., MMR, varicella).
* **History of severe allergic reaction (anaphylaxis) to a previous dose or a vaccine component.**
* **Specific contraindications for certain vaccines:** e.g., severe egg allergy for some influenza vaccines, history of intussusception for rotavirus vaccine.
## Adverse Effects
Commonly include mild, transient symptoms such as low-grade fever, rash (e.g., measles-like rash after MMR or varicella), or injection site reactions. Less common but serious adverse effects can include febrile seizures, thrombocytopenia, or encephalitis (rare).
## Key Drug Interactions
* **Immunosuppressive medications:** Can reduce the immunogenicity of attenuated vaccines. Vaccination should ideally be deferred until the completion of immunosuppressive therapy and the immune system has recovered. If deferral is not possible, discuss with infectious disease specialist.
* **Other live vaccines:** Some live vaccines may interfere with each other if administered simultaneously. Recommendations exist for the order and spacing of administration, or they may be given on the same day.
* **Antibody-containing products:** Administration of blood products (e.g., immunoglobulin, whole blood, packed red blood cells) within a certain timeframe before or after live vaccine administration may interfere with the immune response.
## Monitoring
* Monitor for signs of allergic reaction immediately following administration.
* Educate patients and caregivers on expected common side effects and when to seek medical attention.
* Document vaccine administration, including lot number and manufacturer.
## Clinical Pearls
* While rare, individuals receiving live attenuated vaccines can shed the vaccine virus and potentially transmit it to immunocompromised contacts. Precautions are necessary for individuals receiving the varicella or oral polio vaccine.
* The immunogenicity of live vaccines can be reduced in patients with certain medical conditions or receiving specific therapies; consult current guidelines for management.
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*This information is intended for clinical use and does not substitute for professional medical advice. Always consult the most current prescribing information and relevant guidelines before administering any medication or vaccine.*
