What gauge needle is recommended for intramuscular (IM) flu shot administration in children?

Needle Gauge for IM Flu Shots in Children

For intramuscular influenza vaccination in children, use a 22-25 gauge needle, with needle length being more critical than gauge—25 mm needles are recommended over 16 mm needles for infants and young children to reduce local reactions while maintaining comparable immune response. 1

Needle Gauge Recommendations

The CDC and ACIP guidelines do not specify an exact gauge requirement for pediatric influenza vaccination, but defer to the General Best Practice Guidelines for Immunization for needle selection. 1 However, research evidence provides clear guidance:

• 22-25 gauge needles are appropriate for pediatric IM influenza vaccination, with most studies using either 23 G or 25 G needles. 2, 3
• The gauge (diameter) has minimal impact on vaccine immunogenicity or local reactions compared to needle length. 2
• A 23 G needle (wider) may produce slightly less procedural pain and crying compared to a 25 G needle (narrower), but the clinical difference is negligible. 2

Needle Length: The More Important Variable

Needle length matters far more than gauge for reducing adverse reactions:

• Use 25 mm (1 inch) needles rather than 16 mm needles for infants and young children receiving IM vaccines in the anterolateral thigh. 2, 3
• The 25 mm needle reduces severe local reactions (extensive redness and swelling) with a number needed to treat of 25—meaning one fewer infant experiences severe reaction for every 25 vaccinated with the longer needle. 2
• The 25 mm needle reduces non-severe local reactions (any redness, swelling, tenderness) with NNT of 5-8 after each vaccine dose. 2
• These benefits occur while maintaining equivalent immune response to the vaccine. 2

Injection Site Selection by Age

Site selection is critical and age-dependent:

• Infants and young children: Use the anterolateral aspect of the thigh as the preferred site. 1, 4, 5
• Older children and adolescents: Use the deltoid muscle. 1, 4
• The deltoid should not be used in infants due to insufficient muscle mass. 5

Injection Technique

Proper technique ensures intramuscular delivery:

• Insert the needle at a 90-degree angle to the skin surface. 4, 5
• Use the WHO injection technique: stretch skin flat, insert needle at 90°, and advance up to the needle hub in healthy infants. 2
• Aspiration is not required before injection, as no large blood vessels exist at recommended injection sites. 6

Common Pitfalls to Avoid

• Do not use 16 mm needles when 25 mm needles are available—the shorter needles significantly increase local reaction rates in infants. 2, 3
• Do not assume gauge is the primary determinant of adverse reactions—length is far more important. 2, 3
• Do not use the deltoid in infants—insufficient muscle mass makes this site inappropriate. 5
• Ensure the correct dose volume (0.25 mL or 0.5 mL depending on age and product) is administered, as this is distinct from needle selection. 1

Evidence Quality Note

The evidence supporting 25 mm needle use comes from moderate-quality randomized trials involving over 1,100 infants receiving DTwP vaccines. 2 While these vaccines contain reactogenic whole-cell pertussis components (more reactive than modern influenza vaccines), the mechanical principles of needle length reducing local reactions by ensuring true intramuscular delivery apply across vaccine types. 2, 3