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Emergency And Acute Medicine – Immunizations
Basics
Description Immunization enhances resistance to infectious diseases through passive or active mechanisms. Passive immunization involves administration of antibodies or maternal antibody transfer via placenta or breast milk. Active immunization stimulates the immune system, producing IgM antibodies within 7–10 days followed by IgG antibodies peaking at 2–6 weeks. Oral and nasal vaccines induce mucosal IgA, whereas parenteral vaccines primarily induce systemic immunity. Improper storage, dosing, or administration route can reduce effectiveness.
Etiology
Live attenuated vaccines (e.g., measles, mumps, rubella, varicella, rotavirus) replicate in the host and may cause severe disease in immunocompromised patients. Inactivated vaccines (e.g., IPV, hepatitis A, influenza, pertussis) are safe in immunocompromised patients. Toxoid, subunit, and conjugate vaccines (e.g., tetanus, diphtheria, Hib, pneumococcus, meningococcus, HPV) use antigenic components to stimulate immunity. Hepatitis B vaccines are produced using recombinant DNA technology. Combination vaccines reduce injection burden but increase cost.
Epidemiology
Widespread immunization has markedly reduced many life-threatening infections. Polio has been eliminated from the Western Hemisphere. Hib, diphtheria, and tetanus are now rare in North America. Measles, rubella, and varicella persist mainly in unimmunized populations and travelers. Conjugate pneumococcal vaccines have reduced invasive disease by more than 90% for vaccine serotypes. Rotavirus vaccines reduce severe gastroenteritis. Annual influenza vaccines are produced based on global surveillance. Immunization schedules are tailored by age, pregnancy status, comorbidities, travel, occupation, and immune status.
Diagnosis
Signs And Symptoms Adverse events are usually mild and self-limited. Common reactions include local pain, swelling, erythema, and low-grade fever. Fever is seen after rotavirus, pneumococcal, HPV, MMR/MMRV, meningococcal, and influenza vaccines. Rash may follow varicella or MMR vaccines. Neurologic adverse events are rare and include febrile seizures, hypotonic–hyporesponsive episodes, and very rarely encephalopathy or Guillain–Barré syndrome. Gastrointestinal symptoms may occur after rotavirus vaccine. Live attenuated intranasal influenza vaccine may cause mild respiratory symptoms.
Essential Workup
Review immunization status during ED visits. Determine reasons for incomplete vaccination. Identify true contraindications, including prior anaphylaxis to a vaccine or specific components (e.g., yeast for HepB, egg protein for influenza, neomycin or gelatin for MMR). Assess for conditions requiring deferral, such as moderate to severe acute illness, immunodeficiency, pregnancy (for live vaccines), or recent immune globulin administration.
Treatment
Prehospital And Initial Stabilization Focus on airway, breathing, and circulation.
Emergency Department Management Treat anaphylaxis with epinephrine, antihistamines, bronchodilators, and IV fluids. Manage local reactions with cold compresses and analgesics. Treat fever, myalgias, and arthralgias with acetaminophen or ibuprofen. Manage seizures with benzodiazepines. Provide active or passive immunization as indicated for wound management or exposure prophylaxis. Avoid salicylates for 6 weeks after varicella vaccination in children.
Medication
Acetaminophen 15 mg/kg/dose PO q4–6h.
Ibuprofen 10 mg/kg/dose PO q6–8h.
Follow-Up And Disposition
Admission Criteria Serious adverse reactions such as anaphylaxis, encephalopathy, or severe neurologic symptoms.
Discharge Criteria Routine postimmunization reactions without complications.
Follow-Up Recommendations Arrange primary care follow-up to complete immunization schedules. Report unexpected adverse events to the Vaccine Adverse Event Reporting System.
Key Points And Cautions
Most vaccine reactions are mild and self-limited. True contraindications are rare. Failure to recognize contraindications or to continue antihistamines after allergic reactions may lead to complications. Immunization remains one of the most effective preventive interventions in emergency and acute medicine.
Basics
Description Immunization enhances resistance to infectious diseases through passive or active mechanisms. Passive immunization involves administration of antibodies or maternal antibody transfer via placenta or breast milk. Active immunization stimulates the immune system, producing IgM antibodies within 7–10 days followed by IgG antibodies peaking at 2–6 weeks. Oral and nasal vaccines induce mucosal IgA, whereas parenteral vaccines primarily induce systemic immunity. Improper storage, dosing, or administration route can reduce effectiveness.
Etiology
Live attenuated vaccines (e.g., measles, mumps, rubella, varicella, rotavirus) replicate in the host and may cause severe disease in immunocompromised patients. Inactivated vaccines (e.g., IPV, hepatitis A, influenza, pertussis) are safe in immunocompromised patients. Toxoid, subunit, and conjugate vaccines (e.g., tetanus, diphtheria, Hib, pneumococcus, meningococcus, HPV) use antigenic components to stimulate immunity. Hepatitis B vaccines are produced using recombinant DNA technology. Combination vaccines reduce injection burden but increase cost.
Epidemiology
Widespread immunization has markedly reduced many life-threatening infections. Polio has been eliminated from the Western Hemisphere. Hib, diphtheria, and tetanus are now rare in North America. Measles, rubella, and varicella persist mainly in unimmunized populations and travelers. Conjugate pneumococcal vaccines have reduced invasive disease by more than 90% for vaccine serotypes. Rotavirus vaccines reduce severe gastroenteritis. Annual influenza vaccines are produced based on global surveillance. Immunization schedules are tailored by age, pregnancy status, comorbidities, travel, occupation, and immune status.
Diagnosis
Signs And Symptoms Adverse events are usually mild and self-limited. Common reactions include local pain, swelling, erythema, and low-grade fever. Fever is seen after rotavirus, pneumococcal, HPV, MMR/MMRV, meningococcal, and influenza vaccines. Rash may follow varicella or MMR vaccines. Neurologic adverse events are rare and include febrile seizures, hypotonic–hyporesponsive episodes, and very rarely encephalopathy or Guillain–Barré syndrome. Gastrointestinal symptoms may occur after rotavirus vaccine. Live attenuated intranasal influenza vaccine may cause mild respiratory symptoms.
Essential Workup
Review immunization status during ED visits. Determine reasons for incomplete vaccination. Identify true contraindications, including prior anaphylaxis to a vaccine or specific components (e.g., yeast for HepB, egg protein for influenza, neomycin or gelatin for MMR). Assess for conditions requiring deferral, such as moderate to severe acute illness, immunodeficiency, pregnancy (for live vaccines), or recent immune globulin administration.
Treatment
Prehospital And Initial Stabilization Focus on airway, breathing, and circulation.
Emergency Department Management Treat anaphylaxis with epinephrine, antihistamines, bronchodilators, and IV fluids. Manage local reactions with cold compresses and analgesics. Treat fever, myalgias, and arthralgias with acetaminophen or ibuprofen. Manage seizures with benzodiazepines. Provide active or passive immunization as indicated for wound management or exposure prophylaxis. Avoid salicylates for 6 weeks after varicella vaccination in children.
Medication
Acetaminophen 15 mg/kg/dose PO q4–6h.
Ibuprofen 10 mg/kg/dose PO q6–8h.
Follow-Up And Disposition
Admission Criteria Serious adverse reactions such as anaphylaxis, encephalopathy, or severe neurologic symptoms.
Discharge Criteria Routine postimmunization reactions without complications.
Follow-Up Recommendations Arrange primary care follow-up to complete immunization schedules. Report unexpected adverse events to the Vaccine Adverse Event Reporting System.
Key Points And Cautions
Most vaccine reactions are mild and self-limited. True contraindications are rare. Failure to recognize contraindications or to continue antihistamines after allergic reactions may lead to complications. Immunization remains one of the most effective preventive interventions in emergency and acute medicine.
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