Influenza (flu) is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. The flu is different from a cold. The flu usually comes on suddenly. People who have the flu often experience fever, chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, and fatigue (tiredness). Some people may have vomiting and diarrhea, though this is more common in children than adults.

Some people, such as senior citizens, young children, and people with certain health conditions, are at high risk for serious flu complications. The best way to prevent the flu is by getting vaccinated each year with a flu shot.


The "flu shot" is an inactivated vaccine (containing killed virus) that's given with a needle, usually in the arm.

This season's vaccine protects against the three influenza viruses that research indicates will be most common during the season. This includes an influenza A (H1N1) virus, an influenza A (H3N2) virus, and an influenza B (Hib) virus.

The vaccine takes effect approximately two weeks after it has been administered as antibodies (substances in the blood that protect against infection) accumulate and provide protection against influenza. Therefore, you may be susceptible to influenza during the two weeks after your flu shot.


Seniors ages 65 and older have a higher risk for developing complications from the flu and account for more than 60% of the flu-related hospitalizations each year. Recent studies show that people ages 65+ may not respond as well to standard-dose flu shots because they do not produce as high of an antibody response following vaccination as do younger people. People with low antibody levels may be at higher risk of catching the flu.

Fluzone High-Dose vaccine is designed specifically for patients ages 65+ and works by improving the production of antibodies in order to provide a stronger immune response to the flu than traditional vaccines. Like the standard flu shot, Fluzone High-Dose is given as an injection in the arm and the side effects are similar, though some patients may experience increased redness around the injection site.


The CDC recommends everyone ages 6 months and older* get a flu shot this season, including healthy people, and people with chronic conditions. In general, it is recommended that anyone who wants to reduce his or her chances of getting the flu should be vaccinated. It's especially important for some people to get vaccinated, including:

  • People who are at high risk of developing serious complications like pneumonia if they get sick with the flu. This includes: people who have certain medical conditions including asthma, diabetes, and chronic lung disease
  • Pregnant women
  • People 65 years and older
  • People who live with or care for others who are at high risk for developing serious complications. This includes household contacts and caregivers of people with certain medical conditions including asthma, diabetes, and chronic lung disease.


Certain individuals should not be vaccinated without first consulting a healthcare professional. These patients include:

  • Those with a severe allergy to chicken eggs
  • Those with allergies to certain medications and preservatives, including certain antibiotics and Thimerosal (preservative)
  • Those who have had a severe reaction to an influenza vaccination in the past
  • Those who have had Guillain-Barré Syndrome (GBS) within six weeks of getting the flu vaccine previously
  • Those who have a moderate or severe illness with a fever should wait until they recover before getting a flu shot


The viruses in the flu shot are killed (inactivated), so you cannot get the flu from a flu shot. Some minor side effects that could occur are:

  • Soreness
  • Redness
  • Swelling where the shot was given
  • Fever (low grade)
  • Aches

If these problems occur, they begin soon after the shot and usually last 1 to 2 days. Almost all people who receive influenza vaccine have no serious problems from it.


FluMist Intranasal Spray vaccine is a live virus vaccine which is sprayed into the nose to help protect against influenza. It is a painless and effective alternative to the flu shot. The nasal spray flu vaccine is approved for use only in healthy children, adolescents, and adults ages 2 through 49 years of age who are not pregnant. The nasal spray flu vaccine can be given to people with minor illnesses (e.g., diarrhea or mild upper respiratory tract infection with or without fever). However, the patient should consider delaying getting the vaccine if (s)he has nasal congestion since it may limit delivery of the vaccine to the nasal lining. Patients who sneeze or wipe their nose after getting FluMist do not need to be revaccinated.

This vaccine cannot be given to the following patient types:

  • Pregnant women
  • Patients with a medical condition that places them at high risk for complications from influenza including: those with chronic heart or lung disease, such as asthma or reactive airways disease; people with medical conditions such as diabetes or kidney failure; or people with illnesses that weaken the immune system, or who take medications that can weaken the immune system.
  • Swelling where the shot was given
  • Fever (low grade)
  • Aches

Flu Mist Intranasal Spray vaccine protects against four influenza viruses unlike the flu shot which provides protection against three. The four viruses are two influenza A viruses (H1N1, H3N2), and two B viruses.

Individuals who are vaccinated with live virus vaccines should avoid close contact with anyone who is severely immune compromised.

Call the Centers for Disease Control and Prevention (CDC) at 800-232-4636 or visit the CDC website, at cdc.gov/vaccines, for more vaccine information.


Atkinson W, Hamborsky J, McIntyre L, Wolfe S, eds. Centers for Disease Control and Prevention (CDC).Epidemiology and Prevention of Vaccine-Preventable Diseases. 10th ed. Washington, DC: Public Health Foundation, 2007.

Vaccine Information Statement: Influenza Vaccine (Live, Intranasal). Centers for Disease Control and Prevention (CDC). July 2, 2012.

Center for Disease Control (CDC). Accessed April 2013.