Influenza Vaccine Should Not Be Administered in the Buttocks
The influenza vaccine should not be administered in the buttocks due to potential reduced immunogenicity and risk of sciatic nerve injury. 1
Recommended Injection Sites for Influenza Vaccine
The intramuscular route is recommended for influenza vaccine administration, with specific anatomical sites based on age 1:
The Advisory Committee on Immunization Practices (ACIP) explicitly states that the buttock should not be used for administration of vaccines or toxoids due to two major concerns 1:
- Potential risk of injury to the sciatic nerve
- Decreased immunogenicity of vaccines when administered in the buttock
Scientific Rationale Against Buttock Injections
Injection into the buttock has been associated with decreased immunogenicity of vaccines, presumably because of inadvertent subcutaneous injection or injection into deep fat tissue 1
Research shows that the majority (68%) of intended intramuscular injections into the buttocks actually end up being subcutaneous rather than intramuscular, with only 32% truly reaching muscle tissue 2
The problem is particularly pronounced in females, where only 8% of intended intramuscular buttock injections actually reach the muscle, compared to 56% in males 2
Proper Needle Selection and Technique
For adults and older children receiving deltoid injections, a needle length >1 inch should be used to ensure proper muscle penetration 1
For infants receiving anterolateral thigh injections, ACIP recommends a needle length of 7/8-1 inch 1
Injections must be administered at a 90-degree angle to ensure proper intramuscular placement 1
Importance of Proper Administration
Deviation from the recommended route of administration might reduce vaccine efficacy or increase local adverse reactions 1
Proper intramuscular administration ensures optimal immune response to the influenza vaccine 1
The effectiveness of influenza vaccines varies by season but can provide substantial protection against influenza illness and complications when properly administered 3, 4
Common Side Effects of Properly Administered Influenza Vaccine
Local reactions at the injection site (soreness, redness) are common but typically mild and short-lasting (10-64% of patients) 1
Systemic reactions like fever, malaise, and myalgia may occur, particularly in those with no prior exposure to influenza virus antigens 1
When educating patients about potential side effects, clinicians should emphasize that inactivated influenza vaccine cannot cause influenza, and that coincidental respiratory disease unrelated to vaccination may occur after vaccination 1