FACTS ABOUT INFLUENZA

What is influenza?
Influenza (flu) is a highly contagious viral infection of the nose, throat and lungs that is one of the most severe illnesses of the winter season. Influenza is caused by a virus called the influenza virus. There are three types of influenza viruses: influenza A, B and C. Influenza A can infect humans and other animals while influenza B and C infect only humans. Influenza C virus causes a very mild illness and does not cause epidemics. Influenza is spread easily from person to person, primarily when an infected person coughs or sneezes. Influenza may lead to hospitalization or even death, especially among the elderly.

Typical influenza illness is characterized by the abrupt onset of high fever, chills, a dry cough, headache, runny nose, sore throat and muscle and joint pain. Unlike other common respiratory infections which are often called "the flu", influenza can cause extreme fatigue lasting several days to weeks.

Who is at risk?
Everyone is at risk for contracting influenza. Influenza and its complications can be especially harmful for people 65 years of age and older, and for those who suffer from chronic lung or heart problems (including asthma), chronic metabolic diseases (including diabetes mellitus), renal dysfunction, hemoglobinopathies (such as sickle cell disease), or immunosuppression. The most common complication of influenza is pneumonia.

How significant is influenza?
In the average year, influenza is associated with over 20,000 deaths nationwide and about 110,000 hospitalizations. According to the Centers for Disease Control and Prevention (CDC), it is estimated that during most influenza seasons, approximately 10 to 20 percent of the population is infected with influenza, although rates of infection vary among different age groups and from one season to another. Approximately one percent of those infected will require hospitalization; among those, as many as eight percent will die.

Can influenza be prevented?
The best protection against influenza is an annual influenza shot. Virtually anyone who wants to avoid contracting the flu can receive a shot. For those who cannot take an influenza shot, certain medications are available to help prevent influenza.

When is the best time to get vaccinated?
It takes approximately two weeks after vaccination to develop antibodies against influenza to provide protection. Influenza season generally begins in December and peaks between January and March. During a normal influenza season, the best time to get vaccinated is usually early October to mid-November. Due to expected delays in influenza vaccine supply for the 2000-2001 season, the CDC has issued new recommendations for this season only. The CDC recommends that, as vaccine first becomes available, vaccination efforts should be focused on persons at high risk for complications associated with influenza disease and on health care workers and caregivers who have contact with these persons. Special efforts should be made in December and later to immunize persons 50-64 years of age who are not at high risk and are not household contacts of high risk persons. The CDC also recommends that mass vaccination campaigns should be postponed until later in the season.

How has vaccination proved effective?
According to the CDC, the influenza vaccine has been shown to reduce hospitalization by about 70 percent and death by about 85 percent in the free-living elderly. Among nursing home residents, vaccine can reduce the risk of hospitalization by about 50 percent, the risk of pneumonia by about 60 percent and the risk of death by 75 to 80 percent.

Why is it necessary to get a new vaccine every year?
Different influenza strains circulate every flu season. Based on government recommendations, manufacturers develop each year's vaccine with the three strains of influenza that scientists have predicted to be most common in the coming flu season. The strains from one year's vaccine can not offer immunity to the strains that predominate the following year. Also, immunity to influenza induced by vaccination will decrease over a period of months. Therefore, in order to be properly protected, it is necessary to get vaccinated every year.

Who should be vaccinated?
For the 2000-2001 season, priority vaccination is recommended for persons who are considered to be at high risk for complications associated with influenza disease and for healthcare workers in contact with these persons.

High-risk groups include:

• Persons who are 65 years of age or older
• Residents of nursing homes and other facilities housing patients with chronic medical conditions
• Persons who have chronic disorders of the pulmonary or cardiovascular sustems, including asthma
• Persons how have required regular medical follow-up during the preceding year because of chronic metabolic diseases (including diabetes), renal dysfunction, hemoglobinopathies, or immunosuppression
• Persons aged six months to 18 years who are receiving lon-term aspirin therapy
• Women how will be in second or third trimester of pregnancy during the flu season

CDC's Advisory Commitee on Immunization Practices (ACIP) has issued the following recommendations in response to delays in vaccine supply:

1. When influenza vaccine becomes available, vaccination efforts should be focuses on persons at high risk of complications associated with influenza disease and on health care workers who care for these persons.
   
   
2. Temporary shortages because of delayed or partial shipments may require decisions on how to prioritize use of vaccine available early in the season among high-risk persons and health care workers; such decisions are best made by those familiar with the local situation.
   
   
3. Mass vaccination campaigns should be scheduled later in the season as availability of vaccine is assured. Given projected vaccine distribution, in most areas, campaigns will be scheduled in November or later. Efforts should be made to increase participation by high-risk persons and their household contracts, but other persons should not be turned away.
   
   
4. Groups implementing mass vaccination efforts should seek to enhance coverage among those at greatest risk for complications of influenza and their household contracts. Strategies for targeting mass vaccination efforts at high-risk persons included 1) targeting announcements in publications and other media focused toward the elderly and those with high-risk medical conditions; 2) establishing liaisons with community groups representing the elderly and those with chronic diseases; and 3) offering vaccination to elderly relatives of persons in the workplace and employees.
   
   
5. Special efforts should be undertaken in Decemeber and later to vaccinate persons 50-64 years of age, including those who are not at high risk and are not household contacts of high-risk persons. However, special efforts to vaccinate healthy persons in this age group should begin in December and continue as long as vaccine is available.
   
   
6. Vaccination efforts for all groups should continue into December and later, as long as influenza vaccine is available. Production of influenza vaccine will continue through December, and providers should plan for how vaccine provided late in the season can be used effectively. Vaccination providers who administer all of their available influenza vaccine supply early in the season and who still have unvaccinated high-risk patients should order additional vaccine as it becomes available in December. To minimize wastage of influenza vaccine, providers whose intitial vaccine orders are delayed or partially filled should not seek replacement vaccine from other manufacturers or distributors unless use of all vaccine doses ordered can be assured during the 2000-2001 season.
   
   
7. Pneumococcal vaccines are recommeded by ACIP for many of the same high-risk persons for whom influenza vaccine is recommeded. Assuring pneimococcal vaccination of high-risk persons early in the influenza season will confer substantial protection from a major complication of influenza (pneumoccal pneumonia). Pneumococcal vaccine should be administered when indicated even if influenza vaccine is not yet available. Providers should emphasize to patients or their cargivers that pneumococcal vaccination is not a substitute for influenza vaccination and that patients need to return for influenza vaccine when it is available.
   
   These recommendations were issued for the 2000-2001 season. However, in any flu season, vaccination is generally recommended for all persons 50 years and older and persons at high risk for developing complications from the disease. Earlier this year, ACIP voted to lower the recommended age for influenza vaccination from 64 years of age to 50 years of age and older. Vaccination is also recommended for groups that can transmit influenza to persons at high risk, such as health care workers and employees of nursing homes who have contact with patients or residents. In addition, vaccination is usually recommended for anyone who wishes to avoid flu.
   
   

What are the side effects of the vaccine?
The most common type of side effect is soreness at the injection site. Soreness can last up to two days, is mild, and rarely will impair daily activities.

Fever, malaise, muscle aches, and other symptoms can occur in persons with no previous exposure to the influenza virus used to make the vaccines, for example in children. Symptoms occur 6-12 hours following influenza vaccination and usually last one or two days. Recent studies in elderly persons and healthy young adults, using a type of vaccine called "split-virus influenza vaccine," show no increase in these symptoms.

In addition to the side effects noted above, a number of other rare side effects may occur. Allergic reactions may rarely occur after influenza vaccination and are thought to be due to small amounts of egg protein which may remain in the vaccine after purification. If you are allergic to eggs you are at risk of developing an allergic reaction to the vaccine (see below).

Guillain-Barre Syndrome (GBS) is a condition affecting the nervous system which results in paralysis. Recovery is complete or nearly complete in about 85 percent of cases. An average of six percent of persons with GBS will die. The cause of GBS is unknown and about 10 to 20 cases per one million adults occur each year in the United States. The precise risk of GBS associated with current influenza vaccinations is unclear, but some studies estimate that the risk may be one to two cases per one million vaccinations. Since the annual rate of influenza related complications is so high, the potential benefits of influenza vaccination clearly outweigh the small possible risks of vaccine-associated GBS.

Who should not get the vaccine?
Individuals with egg allergies or those who have had a previous vaccine-associated allergic reaction should avoid immunization. Adults with acute febrile illnesses should usually wait until their symptoms abate before seeking vaccination. However, vaccine may be given in the presence of minor illnesses, with or without fever, particularly among children with mild upper respiratory tract infections or allergic rhinitis. Influenza immunization should also be avoided if a previous flu shot was thought to result in Guillain-Barre Syndrome.

What Strains Does This Year's Flu Vaccine Include?
Each year a new flu vaccine is formulated to protect against new flu strains. The 2000-2001 flu vaccine protects against two new flu strains, which are types A/Panama and A/New Caledonia. The vaccine also includes the B/Yamanashi strain used in last year's vaccine.

Can influenza be treated?
Symptoms of influenza are treated with antipyretics, fluids, and rest. Certain antiviral medications are available to treat influenza infection, but they must be used within 48 hours of onset of symptoms to be effective.

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