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Do You Need a Flu Shot?

Vital Healthcare Group

Do you need a flu shot? If so, should you get the traditional flu shot or FluMist, a nasal-spray flu vaccine?

What is the "flu shot"?

The "flu shot" is an inactivated vaccine (containing killed virus) that is given with a needle, usually in the arm. The flu shot is approved for use among people 6 months of age or older, including healthy people and those with chronic medical conditions (such as asthma, diabetes, or heart disease). What is the nasal-spray flu vaccine? A different kind of vaccine, called the nasal-spray flu vaccine (sometimes referred to as LAIV for Live Attenuated Influenza Vaccine or FluMist®), was approved in 2003. The nasal-spray flu vaccine contains attenuated (weakened) live viruses, and is administered by nasal sprayer.

Each of the two types of seasonal flu vaccines contain three influenza viruses, which are chosen based on information about recently circulating seasonal viruses. Each seasonal influenza vaccine contains - one A (H3N2) virus, one A (H1N1) virus (not the 2009 H1N1 virus), and one B virus. Viruses for both vaccines are grown in eggs. This year, there also is a 2009 H1N1 vaccine. This vaccine is not intended to replace the seasonal flu vaccine - it is intended to be used along-side seasonal flu vaccine.

How do flu vaccines work?

Flu vaccines (the flu shot and the nasal-spray flu vaccine (LAIV)) cause antibodies to develop in the body. These antibodies provide protection against infection with the viruses that are in the vaccine.

Why should people get vaccinated against the flu?

Influenza is a serious disease, and people of any age can get it. In an average year, seasonal flu causes 36,000 flu-related deaths (mostly among those aged 65 years or older) and more than 200,000 flu-related hospitalizations in the United States. The "seasonal flu season" in the United States is usually from November through April each year. During this time, flu viruses are circulating in the population. An annual seasonal flu vaccine (either the flu shot or the nasal-spray flu vaccine) is the best way to reduce the chances that you will get seasonal flu and lessen the chance that you will transmit to others.

When should I get a flu shot?

CDC recommends that people get their seasonal flu vaccine as soon as vaccine becomes available in their community. Vaccination before December is best since this timing ensures that protective antibodies are in place before flu activity is typically at its highest. CDC continues to encourage people to get vaccinated throughout the flu season, which can begin as early as October and last as late as May. Over the course of the flu season, many different influenza viruses can circulate at different times and in different places. As long as flu viruses are still spreading in the community, vaccination can provide protective benefit.

Who should get a flu vaccination?

In general, anyone who wants to reduce their chances of getting seasonal flu can get a seasonal flu vaccine. However, it is recommended by ACIP that certain people should get vaccinated each year. They are either people who are at high risk of having serious seasonal flu-related complications or people who live with or care for those at high risk for serious seasonal flu-related complications. During flu seasons when vaccine supplies are limited or delayed, ACIP makes recommendations regarding priority groups for vaccination.

People who should get the seasonal flu vaccine each year are:
  1. Children aged 6 months up to their 19th birthday
  2. Pregnant women
  3. People 50 years of age and older
  4. People of any age with certain chronic medical conditions
  5. People who live in nursing homes and other long-term care facilities
  6. People who live with or care for those at high risk for complications from flu, including:
    1. Health care workers
    2. Household contacts of persons at high risk for complications from the flu
    3. Household contacts and out of home caregivers of children less than 6 months of age (these children are too young to be vaccinated)
Does getting vaccinated against flu early in the season pose a risk that immunity may wane before the end of the season?

Seasonal flu vaccination provides protection against the seasonal influenza strains contained in the vaccine. Seasonal flu vaccination can begin as soon as vaccine is available. Studies do not show a benefit of receiving more than one dose of vaccine during a flu season, even among elderly persons with weakened immune systems.

Does flu vaccine work right away?

No. It takes about two weeks after vaccination for antibodies to develop in the body and provide protection against influenza virus infection. In the meantime, you are still at risk for getting the flu. That's why it's better to get vaccinated early in the fall, before the flu season really gets under way.

Can I get seasonal flu even though I got a flu vaccine this year?

Yes. The ability of flu vaccine to protect a person depends on two things: 1) the age and health status of the person getting vaccinated, and 2) the similarity or "match" between the virus strains in the vaccine and those circulating in the community. If the viruses in the vaccine and the influenza viruses circulating in the community are closely matched, vaccine effectiveness is higher. If they are not closely matched, vaccine effectiveness can be reduced. However, it's important to remember that even when the viruses are not closely matched, the vaccine can still protect many people and prevent flu-related complications. Such protection is possible because antibodies made in response to the vaccine can provide some protection (called cross-protection) against different, but related strains of influenza viruses.

Why do I need to get vaccinated against the flu every year?

Flu viruses change from year to year, which means two things. First, you can get the flu more than once during your lifetime. The immunity (natural protection that develops against a disease after a person has had that disease) that is built up from having the flu caused by one virus strain doesn't always provide protection when a new strain is circulating. Second, a vaccine made against flu viruses circulating last year may not protect against the newer viruses. That is why the influenza vaccine is updated to include current viruses every year.

Another reason to get flu vaccine every year is that after you get vaccinated your immunity declines over time and may be too low to provide protection after a year.

Source: Centers for Disease Control and Prevention: 2009 H1N1 Flu ("Swine Flu") and You: http://www.cdc.gov/h1n1flu/qa.htm [accessed January 12, 2010]

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