What is the recommended guide for administering an influenza (flu) vaccine?

Guide to Administering Influenza Vaccine

Who Should Receive the Vaccine

Annual influenza vaccination is recommended for all persons aged ≥6 months without contraindications. 1 This universal recommendation applies to children, adolescents, adults, and elderly patients, with particular emphasis on high-risk groups including pregnant women, adults ≥65 years, healthcare workers, and individuals with chronic medical conditions. 2

Priority Groups for Vaccination

• High-risk children and adolescents: Those with asthma, chronic pulmonary/cardiovascular disease, immunosuppression, diabetes, renal dysfunction, hemoglobinopathies, or conditions requiring long-term aspirin therapy 2
• Adults ≥65 years: Should preferentially receive high-dose inactivated (HD-IIV4), recombinant (RIV4), or adjuvanted (aIIV4) formulations 1
• Pregnant women: Should receive inactivated influenza vaccine (IIV) at any time during pregnancy to protect themselves and their infants through transplacental antibody transfer 2
• Healthcare workers and caregivers: All personnel with contact to high-risk persons should be vaccinated to prevent transmission 2

Dosing Schedule

Children 6 Months Through 8 Years

Children in this age group require 2 doses (separated by at least 4 weeks) if they have never received influenza vaccine before or have not received ≥2 total doses before July 1 of the current season. 2, 1 Children who have previously received ≥2 doses of influenza vaccine (even in non-consecutive seasons) require only 1 dose. 2

Children ≥9 Years and Adults

One dose annually is sufficient regardless of vaccination history. 2, 1

Dose Volumes by Age

• 6-35 months: Volume varies by product—Afluria Quadrivalent (0.25 mL), Fluarix/Flucelvax/FluLaval Quadrivalent (0.5 mL), Fluzone Quadrivalent (0.25 mL or 0.5 mL) 1
• ≥36 months through 17 years: 0.5 mL per dose for all inactivated vaccines 1
• Adults 18-64 years: 0.5 mL per dose 3
• Adults ≥65 years: 0.5 mL for most products; 0.7 mL for Fluzone High-Dose Quadrivalent 1, 3

Administration Technique

Injection Site Selection

The deltoid muscle is the preferred site for adults and older children; the anterolateral thigh is preferred for infants and young children. 3 This site selection is based on adequate muscle mass—infants and young children lack sufficient deltoid muscle development. 2, 3

Injection Technique

• Angle: Inject at a 90-degree angle 3
• Needle length: Use appropriate length based on patient size per ACIP General Best Practice Guidelines—typically 7/8-1 inch for children <12 months in the thigh, 7/8-1.25 inches for deltoid in older children, and >1 inch for adults 2, 3
• Aspiration: Not required before injection as no large blood vessels exist at recommended sites 3
• Route: Intramuscular (IM) for inactivated vaccines; intranasal for live attenuated influenza vaccine (LAIV) 1, 3

Common Pitfall

If a smaller dose is inadvertently given to someone requiring 0.5 mL, administer the remaining volume during the same visit. 3

Timing of Vaccination

For most persons requiring only 1 dose, vaccination should ideally occur during September or October. 1 However, vaccination should continue throughout the season as long as influenza viruses are circulating. 1

Special Timing Considerations

• Children requiring 2 doses: Should receive the first dose as soon as vaccine is available, including during July and August, to ensure completion of the 2-dose series before peak influenza season 1
• Adults ≥65 years and pregnant women in first/second trimester: Avoid vaccination during July and August unless there is concern that later vaccination might not be possible 1
• Post-influenza infection: No required waiting period after influenza infection; vaccinate once the child has clinically recovered from acute illness 1

Contraindications and Precautions

Absolute Contraindications

• Severe allergic reaction (anaphylaxis) to any vaccine component or previous dose of any influenza vaccine 2, 3
• Infants <6 months of age 2

Precautions (Not Absolute Contraindications)

• Moderate or severe acute illness with or without fever: Defer vaccination until symptoms abate, though minor illnesses without fever do not contraindicate vaccination 2, 3
• History of Guillain-Barré syndrome within 6 weeks of previous influenza vaccination 3

Egg Allergy Management

Persons with egg allergy may receive any licensed, age-appropriate influenza vaccine without additional precautions beyond those recommended for all vaccines. 2 However, those with severe egg reactions (anaphylaxis) should be vaccinated in a medical setting supervised by a provider able to manage severe allergic reactions. 3

Vaccine Selection

Any licensed, age-appropriate vaccine can be used without preference for one product over another, except for adults ≥65 years who should preferentially receive HD-IIV4, RIV4, or aIIV4. 2, 1 The priority is achieving high vaccination coverage rather than delaying to obtain a specific product. 2

Available Formulations

• Inactivated influenza vaccines (IIV): Administered intramuscularly; can be used for all persons ≥6 months 1, 3
• Live attenuated influenza vaccine (LAIV): Administered intranasally; approved for healthy non-pregnant persons 2-49 years 4
• All vaccines for 2021-2022 and beyond are quadrivalent containing influenza A(H1N1), A(H3N2), B/Victoria, and B/Yamagata components 2

Coadministration with Other Vaccines

Influenza vaccine may be administered simultaneously with or any time before or after other vaccines, including COVID-19 vaccines. 2 Consider the reactogenicity profile when coadministering with COVID-19 vaccines and consult current ACIP/AAP guidance. 2