What is Influenza
How to prevent Influenza
Who should get a Influenza vaccine
When to get a Influenza vaccine
 What is Influenza
Influenza ("flu") is a very contagious disease. It is caused by the influenza virus, which spreads from
infected persons to the nose or throat of others. Other illnesses can have the same symptoms and are often
mistaken for influenza. But only an illness caused by the influenza virus is really influenza.
Anyone can get influenza. For most people, it lasts only a few days. It can cause:
- Fever
- Cough
- Sore throat
- Headache
- Chills
- Muscle aches
- Fatigue
Some people get much sicker. Influenza can lead to pneumonia and can be dangerous for people with heart or
breathing conditions. It can cause high fever and seizures in children. Influenza kills about 36,000 people.
How to prevent Influenza
Influenza vaccine can prevent influenza.
There are two types of Influenza vaccine:
- An inactivated (killed) vaccine, given as a shot, has been used in the United States for many years
- A live, weakened vaccine was licensed in 2003 which is sprayed into the nostrils
Influenza viruses are constantly changing. Therefore, influenza vaccines are updated every year, and an annual
vaccination is recommended. For most people influenza vaccine prevents serious illness caused by the influenza
virus. It will not prevent "influenzalike" illnesses caused by other viruses.
It takes about 2 weeks for protection to develop after the shot, and protection can last up to a year. Inactivated
influenza vaccine may be given at the same time as other vaccines, including pneumococcal vaccine. Some inactivated
influenza vaccine contains thimerosal, a preservative that contains mercury. Some people believe thimerosal may be
related to developmental problems in children. In 2004 the Institute of Medicine published a report concluding that,
based on scientific studies, there is no evidence of such a relationship.
Who should get a Influenza vaccine
Influenza vaccine can be given to people 6 months of age and older. It is recommended for people who are at risk
of serious influenza or its complications, and for people who can spread influenza to those at high risk
(including all household members):
People at high risk for complications from influenza:
- All children 6-23 months of age
- People 65 years of age and older
- Residents of long-term care facilities housing persons with chronic medical conditions
- People who have long-term health problems with:
- Heart disease
- Lung disease
- Kidney disease
- Asthma
- Metabolic disease, such as diabetes
- Anemia, and other blood disorders
- People with certain conditions (such as neuromuscular disorders) that can cause breathing problems
- People with a weakened immune system due to:
- HIV/AIDS or other diseases affecting the immune system
- Long-term treatment with drugs such as steroids
- Cancer treatment with x-rays or drugs
- People 6 months to 18 years of age on long-term aspirin treatment (these people could develop Reye
Syndrome if they got influenza)
- Women who will be pregnant during influenza season
People who can spread influenza to those at high risk:
- Household contacts and out-of-home caretakers of infants from 0-23 months of age
- Physicians, nurses, family members, or anyone else in close contact with people at risk of serious influenza
Influenza vaccine is also recommended for adults 50-64 years of age and anyone else who wants to reduce their
chance of catching influenza.
An annual flu shot should be considered for:
- People who provide essential community services
- People living in dormitories or under other crowded conditions, to prevent outbreaks
- People at high risk of influenza complications who travel to the Southern hemisphere between April and September,
or to the tropics or in organized tourist groups at any time
When to get an Influenza vaccine
The best time to get influenza vaccine is in October or November. Influenza season usually peaks in February, but it
can peak any time from November through May. So getting the vaccine in December, or even later, can be beneficial
in most years.
Some people should get their flu shot in October or earlier:
- People 50 years of age and older
- Younger people at high risk from influenza and its complications (including children 6 through 23 months of age)
- Household contacts of people at high risk
- Healthcare workers,
- Children younger than 9 years of age getting influenza vaccine for the first time
Most people need one flu shot each year. Children younger than 9 years of age getting influenza vaccine for the first
time should get 2 doses, given at least one month apart.
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