An influenza vaccine protects people against the flu.
Vaccine - influenza; Immunization - influenza; Flu shot; Flu vaccine
The flu is a contagious respiratory disease caused by an influenza virus. In the U.S., flu outbreaks typically occur in winter months. Symptoms include fever, chills, sore muscles, and cough. Thousands of people in the U.S. die each year from the flu or its complications. Most of those who die are the elderly, young children, or people with compromised immune systems.
See also: Flu
The viruses that typically cause the flu are primarily categorized as influenza type A or type B. Influenza type B does not change much over time, but type A can mutate rapidly. Therefore, a new form of the flu vaccine must be developed each year to protect people against the exact strains that are expected to be most prevalent.
The flu vaccine that will be given during the fall and winter of 2010 - 2011 will also protect everyone against swine (H1N1) flu. There is no separate vaccine for swine flu.
There are two types of flu vaccines: a flu shot and a nasal spray-type vaccine.
The flu shot contains killed (inactive) viruses, so it is not possible to get the flu from this type of vaccine. However, some people do get a low-grade fever for a day or two after the shot as their immune systems gear up to recognize the virus. The flu shot is approved for people age 6 months and older.
A nasal spray-type flu vaccine called FluMist uses a live, weakened virus instead of a dead one like the flu shot. It is approved for healthy people aged 2 to 49 who are not pregnant. The vaccine helps the lining of the nose fight off actual viral infections. It should not be used in those who have asthma or children under age 5 who have repeated wheezing episodes.
Flu vaccines are generally given at the beginning of the "flu season" -- usually late October or early November in the U.S. However, they may be given as late as March, and still provide some benefit.
People traveling to other countries should be aware that the flu may occur at different times.
WHO SHOULD GET THE VACCINE
The Centers for Disease Control and Prevention (CDC) recommends that everyone 6 months and older should receive the flu vaccine. The flu shot is for people age 6 months and older. Some people are more likely to get the flu or to have a severe infection if they catch it. People at risk for more serious flu infections should always get a flu vaccine every year.
Older children and adults only require a single shot each year. However, children under age 9 need two shots 1 month apart the first time they receive flu vaccine or if they have not previously received two doses during one flu season.
The following people should get a flu shot every year.
- Children between the ages of 6 months and 18 years, especially those under 2
- Household contacts and caregivers of children under the age of 6 months (Breastfeeding women may receive the vaccine.)
You should get a flu shot every year if you:
- Are 50 or older
- Are a health care worker or live with a health care worker
- Have chronic lung or heart disease
- Have sickle cell anemia or other hemoglobinopathies
- Live in a nursing home or extended care facilities
- Live with people who have chronic health problems
- Have kidney disease, anemia, severe asthma, diabetes, or chronic liver disease
- Have a weakened immune system (including those with cancer or HIV/AIDS)
- Receive long-term treatment with steroids for any condition
- Are a pregnant woman
- Are a woman who will be pregnant during flu season
Most people achieve protection from the flu approximately 2 weeks after receiving the vaccine.
RISKS AND SIDE EFFECTS
Most people have no side effects from the flu shot. Soreness at the injection site or minor aches and low grade fever may be present for several days.
Unlike the swine flu vaccine used in 1976, flu vaccines in recent years have shown no association with Guillain-Barre syndrome (GBS) in children, and an extremely small increase in the risk of GBS in adults. This risk is far outweighed by the number of severe flu cases prevented by immunization.
As is the case with any drug or vaccine, there is a rare possibility of allergic reaction.
The regular seasonal flu shot has been shown to be safe for pregnant women and their babies. Most people have no side effects from the flu shot. Soreness at the injection site or minor aches and low grade fever may be present for several days.
Normal side effects of the nasal spray flu vaccine include fever, headache, runny nose, vomiting, and some wheezing. Although these symptoms sound like symptoms of the flu, the side effects do not become a severe or life-threatening flu infection.
WHO SHOULD NOT RECEIVE A FLU VACCINE
Some people should not be vaccinated without first talking to their doctor. The vaccine is not approved for people under 6 months of age. In general, you should not get a flu shot if you:
- Had a severe allergic reaction to chickens or egg protein
- Have a fever or illness that is more than "just a cold"
- Had a moderate to severe reaction after a previous flu vaccine
- Developed Guillain-Barre syndrome within 6 weeks after receiving a flu vaccine
If you meet any of the above criteria, ask your doctor if a flu vaccine is safe for you.
Committee on Infectious Diseases. Policy Statement -- Recommendations for prevention and control of influenza in children, 2010-2011. Pediatrics. 2010 Aug 30.
Key facts about seasonal flu vaccine. Centers for Disease Control and Prevention. Accessed October 2, 2010
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.