Influenza (Flu) Prevention


The single best way to protect against the flu is to get vaccinated each fall. Good health habits and antiviral medications are other measures that can help protect against the flu.

There are two types of vaccines:
• The “flu shot”-an inactivated vaccine (containing killed virus) that is given with a needle, usually in the arm. The flu shot is approved for use
in people older than 6 months, including healthy people and people with chronic medical conditions.
• The nasal-spray flu vaccine-a vaccine made with live, weakened flu viruses that do not cause the flu (sometimes called LAIV for “Live
Attenuated Influenza Vaccine”). LAIV is approved for use in healthy people 5 years to 49 years of age who are not pregnant.

Each vaccine contains three influenza viruses-one A (H3N2) virus, one A (H1N1) virus, and one B virus. The viruses in the vaccine change each year based on international surveillance and scientists’ estimations about which types and strains of viruses will circulate in a given year.
About 2 weeks after vaccination, antibodies that provide protection against influenza virus infection develop in the body.

When to Get Vaccinated
October or November is the best time to get vaccinated, but you can still get vaccinated in December and later. Flu season can begin as early as October and last as late as May.

Who Should Get Vaccinated
In general, anyone who wants to reduce their chances of getting the flu can get vaccinated. However, certain people should get vaccinated each year. They are either people who are at high risk of having serious flu complications or people who live with or care for those at high risk for serious complications.

Who Should Not Be Vaccinated
There are some people who should not be vaccinated without first consulting a physician. These include:
• People who have a severe allergy to chicken eggs.
• People who have had a severe reaction to an influenza vaccination in the past.
• People who developed Guillain-Barre syndrome (GBS) within 6 weeks of getting an influenza vaccine previously.
• Influenza vaccine is not approved for use in children less than 6 months of age.
• People who have a moderate or severe illness with a fever should wait to get vaccinated until their symptoms lessen.

Vaccine Effectiveness
The ability of flu vaccine to protect a person depends on the age and health status of the person getting the vaccine, and the similarity or “match” between the virus strains in the vaccine and those in circulation. Testing has shown that both the flu shot and the nasal-spray vaccine are effective at preventing the flu.

Vaccine Side Effects
Different side effects can be associated with the flu shot and LAIV.

The flu shot: The viruses in the flu shot are killed (inactivated), so you cannot get the flu from a flu shot. Some minor side effects that could occur are:
• Soreness, redness, or swelling where the shot was given
• Fever (low grade)
• Aches

If these problems occur, they begin soon after the shot and usually last 1 to 2 days. Almost all people who receive influenza vaccine have no serious problems from it. However, on rare occasions, flu vaccination can cause serious problems, such as severe allergic reactions.

As of July 1, 2005, people who think that they have been injured by the flu shot can file a claim for compensation from the National Vaccine Injury Compensation Program (VICP).

LAIV: The viruses in the nasal-spray vaccine are weakened and do not cause severe symptoms often associated with influenza illness. (In clinical studies, transmission of vaccine viruses to close contacts has occurred only rarely.)

In children, side effects from LAIV can include
• runny nose
• headache
• vomiting
• muscle aches
• fever

In adults, side effects from LAIV can include:
• runny nose
• headache
• sore throat
• cough

Good Health Habits
Good health habits are also an important way to help prevent the flu.
• Avoid close contact.
Avoid close contact with people who are sick. When you are sick, keep your distance from others to protect them from getting sick too.
• Stay home when you are sick.
If possible, stay home from work, school, and errands when you are sick. You will help prevent others from catching your illness.
• Cover your mouth and nose.
Cover your mouth and nose with a tissue when coughing or sneezing. It may prevent those around you from getting sick.
• Clean your hands.
Washing your hands often will help protect you from germs.
• Avoid touching your eyes, nose or mouth.

Germs are often spread when a person touches something that is contaminated with germs and then touches his or her eyes, nose, or mouth.

Three antiviral drugs (amantadine [Symmetrel?], rimantadine [Flumadine?], and oseltamivir [Tamiflu?]) are approved by the Food and Drug Administration (FDA) and are commercially available for use in the United States to prevent influenza. All of these medications are prescription drugs, and a doctor should be consulted before the drugs are used. When used for prevention, they are about 70% to 90% effective in preventing illness in healthy adults.

All of the antiviral drugs may be effective for influenza A viruses. However, only oseltamivir and zanamivir are effective for influenza B viruses.
Antiviral drugs are most often used to help control influenza outbreaks in institutions (e.g., nursing homes, hospitals), where people at high risk for complications from influenza are in close contact with each other. Antivirals also have been used on cruise ships or similar settings to help control influenza outbreaks.

In the event of an influenza outbreak in a home, institution, or community, your doctor may choose to prescribe antivirals to you as a preventive measure, especially if you are at high risk for complications from influenza. Also, if you are in close contact with someone who is considered at high risk for complications, you may be given antiviral drugs to reduce the chances of passing influenza to the high-risk person.

In the event of an outbreak, public health practice is to combine the use of influenza vaccine and antivirals. For example, nursing home residents and staff are given vaccine during an outbreak and also are given antivirals to prevent influenza until the vaccine takes effect (about 2 weeks). This practice continues as long as influenza is occurring in that setting.

When considering the use of antivirals it is important to remember that most healthy people recover from influenza without complications.
People who are at high risk of serious complications from influenza may benefit most from antiviral medications. This includes: people 65 years of age and older, children 12-23 months of age, people with chronic medical conditions (for example, heart or lung disease, diabetes), and pregnant women. (Note that none of the antivirals are approved for use in children less than 1 year of age.)

Although CDC has provided guidelines for health-care professionals on the use of antiviral drugs, your doctor will decide whether you should receive antiviral drugs this season. The guidelines for use of influenza antivirals are not intended as recommendations for use of these medications in other situations, such as outbreaks of new strains of avian influenza.

Side Effects
Among some healthy adults and children, amantadine and rimantadine can cause central nervous system (CNS) side effects such as nervousness, anxiety, difficulty concentrating, and lightheadedness, and gastrointestinal side effects like nausea and loss of appetite. CNS side effects happen more often among persons taking amantadine than among persons taking rimantadine. Among some other persons with long-term illnesses, more serious side effects, such as delirium, hallucinations, agitation, and seizures, can occur. Side effects usually diminish and disappear after 1 week.

Side effects reported most often in those people who took oseltamivir were gastrointestinal (i.e., nausea and vomiting). Nausea and vomiting may be less severe if oseltamivir is taken with food.