• Vaccines are the primary preventive measure against influenza
• Vaccine used should comply with current World Health Organization (WHO) recommendations
  • Annual seasonal influenza vaccination is recommended for all pediatric patients ≥6 months of age
    • Highly recommended for pediatric patients at increased risk for complications (ie patients with asthma, cardiac disease, immunosuppression, neurodevelopmental disorders)

Influenza Vaccine (Injections)

Composition:

• WHO has a global influenza surveillance program
  • The collaborating centers provide early warning system for emerging strains of influenza that have epidemic potential
  • This system is necessary to create effective vaccines that contain the current circulating strains

• Valency & composition depends upon the number & type of strains covered by the vaccine:
  • Trivalent vaccines: contains 2 type A strains & 1 type B strain of influenza
  • Quadrivalent vaccines: contains 2 type A strains & 2 type B strains of influenza
  • Recommended vaccine composition is issued yearly by WHO in March for vaccines used in the southern hemisphere & in October for vaccines in the northern hemisphere

• Equatorial regions will need to use epidemiological considerations to determine which recommendations (March or October) are appropriate for their region

Inactivated Influenza Vaccine [Intramuscular (IM) or Deep Subcutaneous (SC)]

• Uses vaccine composition issued by WHO in March (southern hemisphere) & in October (northern hemisphere)
• Various types of inactivated influenza vaccine have been formulated to increase immunogenicity: split-virion,whole-virion, surface-antigen/adjuvant containing vaccines (eg aluminum, monophosphoryl lipid, virosome)
• If the vaccine used contains the predominant circulating influenza strains, the vaccine can be 70-90% effective in preventing illness in healthy adults
• Patients with concurrent medical conditions may have a reduced rate of severe respiratory illness & death (up to 50%)
  • Main benefit of vaccination in these patients is the prevention of severe consequences of infection rather than preventing uncomplicated illness
• Vaccines that conform to international standards of purity & potency are usually free from systemic side effects

Live, Attenuated Influenza Vaccine (Intranasal)

• Approved in some countries for the following uses:
  • Option for vaccination of healthy persons aged 2-49 years old
  • May be used in healthy individuals aged 2-49 years in close contact with high-risk groups except those in close contact with immunocompromised patients, or children aged 2-4 years diagnosed with asthma or with wheezing episode within the past 12 months