Influenza Vaccination Guidelines

Introduction to Influenza Vaccines

• Influenza vaccines are available in two forms: inactivated influenza vaccines (IIV) and live attenuated influenza vaccines (LAIV), with different side effect profiles and approved age ranges, as noted by the American Academy of Pediatrics and the Centers for Disease Control and Prevention (CDC) 1, 2, 3
• IIV is approved for persons ≥6 months of age, including healthy individuals and those with chronic medical conditions, while LAIV is approved for healthy individuals 2-49 years of age, according to the American Academy of Pediatrics and the American Academy of Family Physicians 1, 4, 5, 6, 7

Vaccine Administration and Composition

• IIV is administered via intramuscular injection and contains killed viruses, whereas LAIV is administered via intranasal spray and contains live, attenuated viruses, as reported by the American Academy of Pediatrics and the CDC 1, 3
• Both vaccines contain antigenically equivalent strains of influenza viruses, but effectiveness varies by season, strain match, and patient population, as stated by the CDC 3

Side Effects and Contraindications

• LAIV may cause mild influenza-like symptoms, including nasal congestion, runny nose, headache, myalgias, and fever, while IIV is contraindicated in individuals with severe egg allergy (anaphylaxis), as noted by the American Academy of Family Physicians, the CDC, and the American Academy of Pediatrics 1, 2, 4, 5, 8
• LAIV has more contraindications due to its live virus nature, including children <2 years, adults ≥50 years, pregnant women, immunocompromised individuals, children with asthma or history of wheezing, and persons taking influenza antiviral medications (within 48 hours), as stated by the American Academy of Family Physicians and the CDC 4, 5, 6, 7

Special Considerations

• For healthy individuals aged 2-49 years without contraindications, both vaccine types are options, with different side effect profiles to consider, as noted by the American Academy of Pediatrics and the CDC 1, 2, 3
• IIV is preferred for close contacts of severely immunocompromised individuals, children under 2 years, adults over 49 years, pregnant women, and immunocompromised individuals, as recommended by the CDC and the American Academy of Pediatrics 5, 7, 9, 1, 4
• Current guidelines allow most patients with egg allergy to receive either vaccine with appropriate precautions, according to the CDC 8
• The CDC advises against administering LAIV to children aged 2-4 years with asthma or wheezing history, and to persons taking influenza antiviral medications (within 48 hours) 5, 6, 7
• Both vaccines require annual administration due to waning immunity and viral antigenic drift, as recommended by the CDC 3
• LAIV is typically more expensive than IIV, and storage requirements differ between vaccine types, which should be considered in vaccine program planning, as noted by the CDC 3

Effectiveness and Comparisons

• Some studies suggest LAIV may provide better protection in children, while IIV may be more consistently effective in adults, according to the CDC 3
• IIV stimulates primarily systemic immunity, whereas LAIV stimulates both local mucosal and systemic immunity, as reported by the CDC 3