The influenza vaccine stimulates an immune response against seasonal flu viruses, offering protection and reducing the risk of severe complications. Proper administration is a multi-step process encompassing patient screening, selection of the correct method, and careful post-vaccination monitoring. Understanding the correct procedures for administering the flu vaccine is crucial for ensuring its safety and effectiveness.
Available Administration Methods
Flu vaccines are primarily delivered through two distinct routes: intramuscular injection and intranasal spray. The inactivated influenza vaccine (IIV) is the standard flu shot, which contains non-living virus particles and is administered into the muscle tissue. This intramuscular injection is approved for all individuals six months of age and older, making it the most broadly used method for seasonal vaccination.
The alternative is the Live Attenuated Influenza Vaccine (LAIV), which is a nasal spray containing a weakened, but live, form of the virus. This method is typically reserved for healthy, non-pregnant individuals between the ages of two and 49 years. Certain health conditions, such as a weakened immune system, long-term heart or lung disease, or a history of asthma or recurrent wheezing in young children, are general contraindications for the LAIV because of the live virus component. For those with underlying medical conditions that increase the risk of severe flu complications, the injected inactivated vaccine is the appropriate choice.
Pre-Vaccination Screening
Screening is performed immediately before administration to confirm patient eligibility and safety. Healthcare providers must review the patient’s current health status and medical history using a comprehensive screening questionnaire. The presence of an acute, moderate, or severe febrile illness usually means vaccination should be deferred until symptoms improve, although minor illnesses without fever do not require a delay.
Screening focuses on identifying severe allergies to vaccine components or previous adverse reactions. While egg allergy is no longer a general contraindication for most flu vaccines, those who experienced a severe systemic or anaphylactic reaction to a previous dose require careful evaluation. A history of Guillain-Barré syndrome (GBS) within six weeks of a prior flu vaccination also warrants discussion with a healthcare provider. Informed consent is obtained after the patient receives a Vaccine Information Statement (VIS) explaining the benefits and risks of the specific vaccine.
Intramuscular Injection Procedure
The intramuscular (IM) injection procedure requires careful attention to needle selection, site location, and technique. For adults and older children, the preferred injection site is the deltoid muscle in the upper arm. The site is identified by locating the acromion process, the bony point of the shoulder, and injecting approximately two to three fingerbreadths below it, into the central and thickest part of the muscle.
The needle gauge is typically 22 to 25, but the appropriate needle length varies based on the recipient’s age and body mass. A longer needle is often necessary to penetrate the subcutaneous fat layer and reach the muscle, particularly in adults; a 1- to 1.5-inch needle is commonly used for most adults. For infants under 12 months of age, the injection is administered into the anterolateral thigh muscle, using a shorter needle, typically 7/8 to 1 inch.
After the site is cleaned, the needle is inserted with a quick, single thrust at a 90-degree angle to the skin. Inserting the needle at a right angle ensures the vaccine is deposited deep into the muscle for the proper immune response. The entire dose is injected, and aspiration (pulling back on the plunger) is not recommended for vaccines. Following the injection, pressure is applied to the site, and the used syringe and needle are immediately disposed of in a designated sharps container.
Post-Vaccination Care
Once the vaccine has been administered, monitoring the patient for immediate adverse events is a standard procedure. All recipients should be observed for a minimum of 15 minutes, as severe allergic reactions, known as anaphylaxis, typically occur rapidly after vaccination. Anaphylaxis is a rare but serious event characterized by signs such as difficulty breathing, hoarseness, hives, swelling, or dizziness.
Common, mild side effects are expected and usually resolve on their own within a few days. These local reactions include soreness, redness, or swelling at the injection site. Some individuals may experience mild systemic symptoms such as a low-grade fever, headache, or muscle aches. Patients are advised that these reactions are normal signs that the body is building protection and are not the flu itself.
Patients should seek immediate medical attention if they experience signs of a severe reaction after leaving the clinic, such as throat swelling or persistent shortness of breath. For less severe but concerning symptoms, they should contact their healthcare provider. Fainting, or a vasovagal episode, is the most common immediate adverse event in older children and adults and is managed by having the patient lie down until symptoms pass.