Influenza (Flu) Vaccine

Influenza, also known as the "flu," is an infection of the respiratory system that is caused by the influenza virus. The flu is spread by coughing and sneezing, and its season peaks between late December and March, although this can vary each year. The flu is responsible for an average of 226,000 hospitalizations and 36,000 deaths every year in the U.S.

Symptoms of the flu typically begin very quickly. Symptoms often include muscle aches, feeling very tired, fever with chills, headache, cough and a sore throat. In addition, children may also have a high fever, diarrhea and seizures. Most people recover from the flu in 1 - 2 weeks. However, some people, especially the very young and the elderly, can have flu-related complications that can be serious.

In some people, the flu can lead to serious complications. Some people develop influenza pneumonia or a secondary bacterial pneumonia. People with asthma and other chronic lung diseases may have worsening of respiratory symptoms that require stronger treatment. They also have a higher risk of developing pneumonia from influenza. Myocarditis and pericarditis, which affect the heart, have also been linked to the flu. Other rare complications include Reye's syndrome, myositis and Guillain-Barre syndrome.

Treatment with antiviral medicine is available when someone gets the flu. These medicines help lessen the symptoms and the length of time a person is ill. Antiviral medicines must be started within the first two days after symptoms begin. These medicines include:

  • Relenza® (zanamivir)
  • Tamiflu® (oseltamivir)

Fortunately, the flu vaccine can prevent many of the illnesses and deaths associated with the flu. The flu vaccine contains either killed or weakened (attenuated) influenza viruses that cause your immune system to develop antibodies.

It takes two weeks to build an adequate level of antibodies to protect against the flu. When you are exposed to the flu, these antibodies then fight off the flu viruses. While the vaccine does not always prevent the flu, the vaccine reduces the risk of complications and the severity of the illness. The protection lasts about one year.

The seasonal flu vaccine is not protective against the 2009 H1N1 Flu


Those Who Should Get the Vaccine

Most people benefit from receiving the flu vaccine. Anyone who would like to decrease the chances of getting the flu or spreading the flu to others can get the flu shot each year. The flu shot is strongly recommended for people who are at high risk for complications of the flu. Also, people who can give the flu to those who are at high risk should be vaccinated.

A yearly flu vaccine is strongly recommended for the following groups:

  • Children and teens age 6 through 18 years
  • Adults age 50 and over
  • Nursing home and long-term care residents
  • People with chronic respiratory diseases such as asthma, COPD (emphysema, chronic bronchitis), cystic fibrosis or bronchiectasis
  • Adults with high-risk conditions such as chronic lung or heart disease, sickle cell anemia or other hemoglobinopathies, cancer, kidney, anemia, diabetes or liver diseases, neurologic/neuromuscular disease
  • People who have a suppressed immune system, including HIV
  • healthcare providers
  • Women who will be pregnant during the flu season
  • People who live with, care for, or have contact with children less than 5 years old and/or adults older than 50 with high risk health issues
  • Household members and child care providers of children less than 6 months of age.

The vaccine is safe for children six months of age and older. The first time children under nine years of age are vaccinated, they should be given two doses one month apart.


When to Get the Vaccine

Each year the flu vaccine is developed with the three main strains of influenza virus. These strains have been identified as the cause for the illness in the upcoming year. The flu vaccine must be given every year for protection against the flu. The best time to receive the vaccine is October through November. The flu vaccine can be given as soon as it becomes available in late August or September. It can also be given later than November.


Types of Flu Vaccines Available this Year

There are two types of influenza vaccines available. One is inactivated influenza vaccine or the standard "flu shot" that contains killed influenza viruses. The other is a live, intranasal influenza vaccine.

Inactivated influenza vaccine: The flu shot has been given for many years and is approved for infants aged 6 months and older, children, teens and adults. It is the preferred vaccine for people who have chronic illness or a weakened immune system, and for healthcare providers and pregnant women.

Live, intranasal influenza vaccine: A nasal spray is also available. It contains live, but weakened (attenuated) viruses. It is recommended for healthy children and adults aged 2 through 49 years.


Side Effects

The flu vaccine is safe for almost everyone. Because the vaccine is made from killed or weakened viruses, a person cannot "get" the flu from the vaccine. Some people experience a few minor side effects from the flu shot. These can include: swelling, redness or soreness at the area of the shot, muscle aches and a low-grade fever for a few days.

Minor side effects from the nasal spray include: runny or stuffy nose, cough, headache and muscle aches, chills, and fever. In addition children and teens may have abdominal pain or occasionally vomiting and diarrhea.

Severe side effects are rare, but include an allergic reaction which may occur several minutes to a few hours after the flu shot.

When the swine flu vaccine was given in 1976, more serious side effects, such as Guillain-Barre Syndrome, were reported. There has been no increased incidence of Guillain-Barre Syndrome since that time.

There has been some concern about reactions to Thimerasol, the preservative in the flu shot. It is used at a very small amount and has not been shown to be a problem. However, if you are concerned about Thimerasol, you can check with your doctor about a "preservative free" flu vaccine.


Those Who Should NOT Get the Vaccine

There are certain groups of people who should check with their doctor before getting a flu vaccine. These include:

  • People who have had a severe reaction to a flu shot in the past,
  • People who developed Guillain-Barre Syndrome 6 weeks after getting a flu shot and,
  • People who have a severe allergy to egg.

Egg Allergy

Because the flu vaccine has been grown on egg protein, the flu vaccine is not recommended for people who have a history of severe egg allergy. However, if you have been able to eat eggs, it may be possible for you to receive the flu vaccine. Many people who believe they are allergic to eggs tolerate the flu vaccine. For some people who are allergic to the vaccine, it can be given in smaller doses under close supervision. This can require several shots over many hours. This is only done when the person is at high risk for complications of the flu.

Please discuss any questions you have about the influenza vaccine or the pneumococcal vaccine with your healthcare provider. The Center for Diseases Control and Prevention (CDC) has helpful Vaccine Information Statements (VIS) at

This information has been approved by Ann Mullen, RN, MS, AE-C (September 2009).

Refer a Patient

Connect with Us Online

Become our fan on facebook!   Subscribe to our YouTube channel!   Follow us on Twitter!   Subscribe to our News RSS feed.  Learn about CarePages, an online support community.

eNewsletters and More

Our Programs

We seek to transform patient care from reactive to being both proactive and personalized.

Directory of Programs & Services