Influenza Vaccination Guidelines for Infants

Vaccine Selection and Dosing

The Centers for Disease Control and Prevention recommends that a 9-month-old child with no prior influenza vaccination history requires 2 doses of trivalent inactivated influenza vaccine (TIV), administered at least 4 weeks apart, with the first dose given as soon as possible 1
For a 9-month-old infant, any licensed, age-appropriate inactivated influenza vaccine (IIV) can be used at the correct volume 2
The specific dose volume depends on the manufacturer's formulation, so verify the product-specific dosing 4, 3

Children aged 6 months through 8 years require 2 doses during their first season of vaccination because they lack prior immune priming to circulating influenza strains, with evidence demonstrating significantly higher protective antibody responses after 2 doses compared to a single dose (p<0.001 for H1N1 and influenza B, p=0.01 for H3N2) 1, 5

The minimum interval between doses is 4 weeks 1, 2
The first dose should be administered as soon as vaccine becomes available, including July and August if available, to ensure the second dose can be completed ideally by the end of October 1
The vaccine should be administered via intramuscular injection in the anterolateral aspect of the thigh (preferred site for infants) 6, 3

Live attenuated influenza vaccine (LAIV) is NOT an option for this patient because it is only approved for persons aged 2 years and older 4, 2
Only inactivated vaccines should be used in children under 2 years of age 7, 2

Injection-site reactions (pain, redness, swelling) occur in approximately 1-3% of cases 6

For subsequent influenza seasons, this child will need only 1 dose annually once they have received at least 2 total doses of influenza vaccine (trivalent or quadrivalent) at least 4 weeks apart before July 1 of the upcoming season 1