Influenza (“Flu”) Vaccine

What is the Influenza (“flu”) Vaccine?

Influenza (“flu”) vaccinations are formulated to prevent infection from influenza viruses. There are three main types of influenza viruses and many subtypes.  Flu season typically runs from late-fall to early-spring and affects approximately 5 – 20% of the U.S. population each year Flu.Gov.  

There are four main types of influenza viruses – A, B C and D.  Most seasonal flu outbreaks are caused by either Influenza A or B.  These types are divided into various sub-types based on two proteins found on the surface of the virus:  Hemagglutnin (H) and Neuroaminidase (N).  It is these surface proteins that contribute to the immune response to the virus.  Most seasonal flu outbreaks are caused by either Influenza A or B.  These flu viruses can cause symptoms, including chills, fever, nasal congestion, sore throat, coughing, headaches, muscles soreness, weakness, fatigue and general discomfort.  Often, these symptoms can be debilitating, requiring several days of bed rest.

The most common seasonal flu vaccination is the quadrivalent vaccine, which is designed to protect against four strains – two strains each of influenza A and B.  The nasal spray version of the quadrivalent vaccine is slightly different in that it contains a live, but weakened version of the virus, and is approved for non-pregnant individuals, aged 2 through 49.  

The high dose trivalent flu vaccination contains four times the antigen of a standard dose inactivated flu vaccine, and is recommended for individuals 65 years of age and older. 

Who should receive the Flu vaccine?

The CDC issues recommendations as to who should receive the flu vaccine.  While the CDC recommends that everyone 6 months of age and older should receive a flu vaccine each year, there are a number of exceptions.  There are also a number of contraindications to receiving the flu vaccine.  For example, you should not be vaccinated if you are currently experiencing flu-like symptoms or have previously experienced a severe reaction like Guillain-Barré Syndrome (GBS) after receiving a flu vaccine.  If you have a chicken or egg protein allergy, you should consult with your doctor before receiving a flu vaccination.

How is the Flu Vaccine administered?

Most flu shots are administered intramuscularly, through the skin, underneath the fatty tissue and into the muscle tissue. All intramuscular flu shots should be injected at a 90-degree angle into the deltoid muscle. If an intramuscular flu shot is injected incorrectly, it can result in a serious shoulder injury.

Intranasal flu vaccines should be administered by having the recipient tilt their head back at a 45-degree angle so that the vaccine can be sprayed into the recipient’s nostril.

Influenza links:                                                                                                     

CDC Inactivated Influenza Information Sheet                                               

CDC Live, Intranasal Information Sheet                                                          

CDC Administration Guidelines                                                              – Influenza