Is the influenza (flu) vaccine the same for children and adults?

Flu Vaccine Differences Between Children and Adults

The flu vaccine is not the same for children and adults, with differences in dosing, formulations, and administration recommendations based on age.

Key Differences in Flu Vaccines by Age

Vaccine Formulations

• All seasonal influenza vaccines are now quadrivalent (containing 4 virus strains) 1
• Children and adults receive vaccines with the same virus strains, but in different formulations 1
• Some vaccines are specifically approved for certain age groups:
  • Live Attenuated Influenza Vaccine (LAIV/nasal spray):
    • Only approved for healthy people 2-49 years of age 1
    • Contraindicated in children under 2 years 1
  • High-dose and adjuvanted vaccines:
    • Only approved for adults ≥65 years 1

Dosing Differences

• Children 6-35 months: May receive specific pediatric formulations with different dosing 1

  • Some vaccines for this age group are available in 0.25 mL doses (Afluria Quadrivalent) 1
  • Others are available in 0.5 mL doses (Fluarix, FluLaval) 1

• Children 6 months through 8 years: May need two doses their first season 1

  • Children receiving flu vaccine for the first time need two doses given at least 4 weeks apart 1
  • Children who have not received ≥2 doses of any influenza vaccine before July 1 of the current year also need two doses 2

• Children 9 years and older and adults: Need only one dose regardless of vaccination history 2

Vaccine Types and Age Restrictions

• Inactivated Influenza Vaccine (IIV):

  • Can be given to anyone 6 months and older 1
  • Available in different formulations for different age groups 1

• Live Attenuated Influenza Vaccine (LAIV/nasal spray):

  • Only for healthy people 2-49 years old 1
  • Contraindicated in children <2 years due to increased risk of wheezing 3
  • Not recommended for children 2-4 years with history of wheezing or reactive airway disease 3

Efficacy Considerations

• Children may develop higher post-vaccination antibody titers than elderly adults 1
• Vaccine effectiveness varies by age:
  • In children, effectiveness ranges from 59-82% depending on vaccine type 1
  • Effectiveness may be lower in children under 2 years 4
  • Older adults may develop lower antibody titers than younger people 1

Clinical Implications and Best Practices

For Healthcare Providers

• Select age-appropriate vaccine formulations based on:

  • Patient age
  • Previous vaccination history
  • Underlying medical conditions

• For children 6 months through 8 years:

  • Check vaccination history to determine if one or two doses are needed
  • Schedule second dose at least 4 weeks after the first if required

• Use the appropriate dose volume based on age and specific vaccine product 1

Important Considerations

• Do not delay vaccination to wait for a specific product - use any age-appropriate vaccine that's available 2
• Annual vaccination is necessary because immunity declines in the year following vaccination 1
• Vaccination is particularly important for high-risk groups, including children <5 years (especially <2 years) and adults ≥65 years 1

Safety Profile

• Most influenza vaccines are generally safe, but some adverse events may differ between children and adults 5
• Fever and febrile seizures are more common in children than adults 5
• Safety of one influenza vaccine in children should not be extrapolated to all influenza vaccines 5

Remember that annual influenza vaccination is recommended for everyone 6 months and older, with specific formulations and dosing schedules tailored to different age groups.