Influenza%20(pediatric) Management

• 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

Influenza Vaccine

• Both inactivated and live attenuated influenza vaccine can be used for the prevention of pediatric influenza
• Quadrivalent vaccines are recommended for all pediatric influenza vaccines 
• Live attenuated influenza vaccine 4 (LAIV4) is an option for patients in whom it is appropriate (≥2 years old, no risk factors for complications, no history of antiviral medication intake within 48 hours or up to 2 weeks if with previous Baloxavir use)
• For individuals with history of egg allergy, the American Academy of Pediatrics (AAP) and ACIP recommend to proceed with administration of influenza vaccine, although ACIP recommends specific situations based on previous symptoms:
  • Presence of hives/urticaria only should not be a contraindication
  • Those who experienced symptoms other than hives (eg angioedema, respiratory distress, lightheadedness, recurrent emesis) and needed Epinephrine or other medical interventions may receive influenza vaccine
  • Severe allergic reaction is a contraindication for vaccination with any form of influenza virus
  • A 15-minute observation period is recommended following administration of any vaccine
  • Patients/guardians who refuse egg-based vaccines may receive recombinant or cell-cultured products
    • Cell culture-based quadrivalent inactivated influenza vaccine may be used for children aged ≥2 years
• Dosing depends on child's age during 1st dose and immunization history
  • Children 6-35 months old may receive either 0.25 mL or 0.5 mL dose
  • Children ≥36 months of age may continue to receive 0.5 mL dose
  • For children 6 months-8 years old:
    • 2 doses ideally by end of October, separated by at least 4 weeks, are needed if <2 doses were received before July 1, 2022 or if vaccination history is unknown
    • 1 dose needed by end of October if already received ≥2 total doses before July 1, 2022
  • Children ≥9 years old require only 1 dose

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

• For the 2022/2023 northern hemisphere flu season, the recommended egg-based trivalent vaccine should contain an A/Victoria/2570/2019 (H1N1)pdm09-like virus, an A/Darwin/9/2021 (H3N2)-like virus and a B/Austria/1359417/2021 (B/Victoria lineage)-like virus     
  • Quadrivalent vaccines will contain above 3 viruses, plus a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus
• For the 2022/2023 northern hemisphere flu season, the recommended cell- or recombinant-based trivalent vaccine should contain an A/Wisconsin/588/2019 (H1N1)pdm09-like virus, an A/Darwin/9/2021 (H3N2)-like virus and a B/Austria/1359417/2021 (B/Victoria lineage)-like virus 
  • Quadrivalent vaccines will contain above 3 viruses, plus a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus
• For the 2023 southern hemisphere flu season, the recommended egg-based trivalent vaccine should contain an A/Sydney/5/2021 (H1N1)pdm09-like virus, an A/Darwin/9/2021 (H3N2)-like virus, and a B/Austria/1359417/2021 (B/Victoria lineage)-like virus
  • Quadrivalent vaccines will contain above 3 antigens, plus a B/Phuket/3073/2013–like virus (B/Yamagata/16/88 lineage)-like virus
• For the 2023 southern hemisphere flu season, the recommended cell- or recombinant-based trivalent vaccine should contain an A/Sydney/5/2021 (H1N1)pdm09-like virus, an A/Darwin/6/2021 (H3N2)-like virus, and a B/Austria/1359417/2021 (B/Victoria lineage)-like virus
  • Quadrivalent vaccines will contain above 3 viruses, plus a B/Phuket/3073/2013 (B/Yamagata lineage)-like virus

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

• Uses vaccine composition issued by WHO in March (northern hemisphere) and in October (southern 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 and 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 and 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 children aged ≥2 years
  • 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

Recommendations for Influenza Vaccination and Coronavirus Disease 2019 (COVID-19)

• Reducing the prevalence of influenza through vaccination may help the symptoms that are confused with those of COVID-19
• For patients with mild or asymptomatic COVID-19, vaccination should be deferred to avoid confusing COVID-19 illness symptoms with postvaccination reactions
• For patients with moderate to severe COVID-19, vaccination should be deferred until fully recovered
• For individuals who are unvaccinated or partially vaccinated against COVID-19 with COVID-19 infection or had close contact exposure with a COVID-19-positive individual, influenza vaccination should be delayed until quarantine or isolation period has been fulfilled
  • Symptomatic individuals should have fully recovered prior to going to a vaccination site
• For patients already admitted in a healthcare facility:
  • Patients who have been fully vaccinated and with no known recent exposure to individuals with suspected or confirmed COVID-19 infection may proceed to receive influenza vaccine
  • Influenza vaccine may be given to patients in quarantine due to close contact exposure with a COVID-19-positive individual if another opportunity to be vaccinated is not likely; vaccination may be deferred until quarantine has been completed if possible symptoms of COVID-19 infection may cause diagnostic confusion
  • Vaccination should be delayed for symptomatic individuals with suspected or confirmed COVID-19 infection until criteria to discontinue isolation is fulfilled (at least 10 days after symptom onset and 24 hours afebrile without the use of fever-reducing medications) and COVID-19 symptoms are improving, and the person is no longer moderately to severely ill
  • Vaccination may be given to asymptomatic or presymptomatic individuals with suspected or confirmed COVID-19 infection, or those who have fully recovered and are now asymptomatic, even if criteria to discontinue isolation has not been fulfilled, especially if another opportunity to be vaccinated is not likely