What is the proper technique for administering an influenza (flu) vaccine?

How to Administer a Flu Shot

For intramuscular influenza vaccination, inject into the deltoid muscle for adults and older children, or the anterolateral thigh for infants and young children, using a 90-degree angle with appropriate needle length, without aspiration. 1

Site Selection by Age

Adults and Older Children

• The deltoid muscle is the recommended injection site for adults and older children receiving intramuscular influenza vaccines 1
• Position the injection at the mid-point of the deltoid muscle (midway between the acromion and deltoid tuberosity) with the arm abducted to 60° 2
• Practical technique: Have the patient place their hand on the ipsilateral hip, then place your index finger on the acromion and thumb on the deltoid tuberosity, injecting at the midpoint between these landmarks 2
• Avoid the upper third of the deltoid muscle to prevent shoulder injury related to vaccine administration (SIRVA), including subdeltoid bursitis and nerve injury 2, 3, 4
• The injection site should be 2 fingerbreadths below the acromion process 5

Infants and Young Children

• The anterolateral aspect of the thigh is the preferred site for infants and young children 1, 6
• This site is recommended due to insufficient deltoid muscle mass in this age group 6
• The deltoid should not be used in infants 6

Dose Volume by Age and Product

Children Aged 6-35 Months

• Fluzone Quadrivalent: Either 0.25 mL or 0.5 mL per dose 1, 6
• FluLaval Quadrivalent: 0.5 mL per dose 1
• Flucelvax Quadrivalent: 0.5 mL per dose 1
• Afluria Quadrivalent: 0.25 mL per dose (must be obtained from multidose vial) 1

Children Aged 36 Months Through 17 Years

• Standard dose: 0.5 mL for all intramuscular IIV4 products 1

Adults Aged 18-64 Years

• Standard dose: 0.5 mL for most products 1

Adults Aged ≥65 Years

• Standard dose: 0.5 mL for most products 1
• Fluzone High-Dose Quadrivalent: 0.7 mL per dose 1

Injection Technique

Needle Selection and Insertion

• Insert the needle at a 90-degree angle to ensure proper intramuscular placement 6
• For adults using a 0.5-inch needle, advance the entire needle length perpendicular to the skin at 2 fingerbreadths below the acromion to ensure deltoid muscle penetration 5
• Use appropriate needle length based on patient size and injection site per ACIP General Best Practice Guidelines 1

Aspiration

• Aspiration is not required before injection of influenza vaccines because no large blood vessels exist at the recommended injection sites 7
• The CDC formally discontinued routine aspiration recommendations for vaccines at standard sites 7

Site Preparation

• Clean the injection site with an alcohol swab before administration 6
• Stabilize the muscle (thigh in infants, deltoid in adults) and inject quickly 6

Dosing Errors and Corrections

Underdosing

• If a smaller dose (e.g., 0.25 mL) is inadvertently given to someone requiring 0.5 mL, administer the remaining volume during the same visit 1
• If the error is discovered after the patient leaves, administer a full 0.5 mL dose as soon as the patient returns 1

Wrong Formulation

• If an adult formulation is inadvertently given to a child, count it as a valid dose 1

Alternative Administration Methods

Jet Injector

• Afluria Quadrivalent may be administered via PharmaJet Stratis jet injector for persons aged 18-64 years only 1
• All other age groups and all other vaccine products must use needle and syringe 1

Intradermal Administration

• Fluzone Intradermal Quadrivalent (when available) is administered intradermally over the deltoid using the included delivery system 1
• This is a distinct product with different dosing (0.1 mL containing 9 μg per strain) 1

Contraindications and Precautions

Absolute Contraindications

• History of severe allergic reaction (e.g., anaphylaxis) to any vaccine component or previous dose of any influenza vaccine 1

Precautions

• Moderate or severe acute illness with or without fever 1
• History of Guillain-Barré syndrome within 6 weeks of previous influenza vaccination 1

Egg Allergy

• Persons with egg allergy may receive any licensed, age-appropriate influenza vaccine 1
• Those with severe egg reactions (beyond urticaria) should be vaccinated in a medical setting supervised by a provider able to manage severe allergic reactions 1

Common Pitfalls to Avoid

• Do not inject too high on the deltoid (upper third of muscle) as this risks subdeltoid bursa injection, causing bursitis and shoulder dysfunction 2, 3, 4
• Do not use the deltoid in infants due to insufficient muscle mass 6
• Do not aspirate before injection—this is unnecessary and outdated practice 7
• Do not confuse dose volume with number of doses—children 6-35 months requiring 2 doses need them ≥4 weeks apart regardless of volume per dose 1