Influenza Virus Vaccination Fact Sheet

Mary Ross, R.Ph., M.B.A., Barbara Mutnick, R.Ph., M.H.P., Joan Murhammer, R.Ph.
Peer Review Status: Internally Reviewed

WHAT IS INFLUENZA ("FLU")? Influenza is a viral infection of the nose, throat, bronchial tubes, and lungs. Flu usually occurs between November and April. The most common symptoms of influenza include a sudden fever (up to 104°F), often accompanied by headache, chills, dry hacking cough, fatigue, and muscle aches of the back, arms, and legs. A runny, stuffy nose, congestion, and sore throat may also be present. Most persons are ill for 3 to 7 days, but some symptoms, like cough and fatigue may last longer than 7 days. Some persons may have a much more serious illness and may require hospitalization. Contrary to popular opinion, influenza is not the common cold or a gastrointestinal disease.

HOW IS IT SPREAD? Primarily by respiratory droplets in the air from coughing, sneezing, or talking, or from hand to hand transmission. The incubation period is from 1 to 5 days. A person is contagious for 2 to 7 days after symptoms appear.

WHO SHOULD GET INFLUENZA VACCINE?

Because of increased risk for serious illness:

• Everyone 65 years of age or older, and children aged 6 to 23 months.
• Adults and children with chronic heart or lung problems, including asthma
• Residents of nursing homes and other chronic-care facilities that house persons who have chronic medical conditions
• Persons who during the past year have regularly seen a doctor or have been admitted to a hospital for treatment for kidney disease, cystic fibrosis, chronic metabolic diseases such as diabetes, anemia, severe asthma, cancer, HIV, or other immunological disorders (or use certain types of medicines) that lower the body's normal resistance to infections
• Children and teenagers (6 months to 18 years of age) who are receiving long-term aspirin therapy, and therefore, may be at risk of developing Reye syndrome after influenza
• Women who will be in the second or third trimester of pregnancy during influenza season

Because of increased risk of spreading the virus:

• Healthcare workers
• Household members (including children) who provide care to the high-risk persons listed above
• Employees of nursing homes, chronic care facilities, and assisted living residences
• Persons who provide home care to persons in high-risk groups

WHAT IS THE DOSAGE?

• Usually a single injection of inactivated (non-infectious) vaccine
• It takes approximately 2 weeks for the vaccine to be effective against influenza
• Annual vaccinations are necessary because viral strains vary from year to year

WHEN SHOULD VACCINATION OCCUR?

• Persons at increased risk for serious illness should receive vaccine as soon as it is available. For other persons, October and November are the best months to receive influenza vaccination. However, persons can still get vaccinated in December, January, and later (as long as the vaccine is available) to receive protection against influenza.

WHAT ARE POSSIBLE SIDE EFFECTS FROM THE VACCINE? The risks from the vaccine are much smaller than the risks from the disease. Today's vaccines are much more purified than earlier vaccines; therefore, there is only a very small risk that a serious problem could occur after taking the vaccine. Most persons who get the influenza vaccine have no side effects. If the following mild or moderate problems occur, they usually last from 1 to 2 days:

• Soreness, redness, or swelling at injection site
• Fever or body aches

WHO SHOULD NOT RECEIVE THE INFLUENZA VACCINE? Persons who:

• Have an anaphylactic hypersensitivity to eggs
• Have had previous serious allergic reaction or other serious problems after getting an influenza vaccination
• Currently have an acute or severe febrile illness

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