The Flu Shot: Q & A

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Flu viruses are constantly changing. Each flu season, different flu viruses can spread, and they can affect people differently based on the virus and on their body's ability to fight infection. Some flu seasons are worse than others, and there is no way to predict how severe the flu season will be. Each year, a new flu vaccine is made from the three viruses that are expected to be present during the season. Two of the three viruses have changed from last season, but the 2009 influenza A/H1N1 virus antigen remains in the 2012-2013 vacccine. (An antigen is the substance that your body recognizes and uses to form protective antibodies.)

Who should get the flu shot?
The Centers for Disease Control and Prevention (CDC) recommends that everyone over age 6 months get the flu vaccine, with important exceptions. People with severe allegy to egg, people who have had a serious reaction to a flu shot in the past, and people who have had a very rare nervous system condition called Guillian-Barre syndrome should not get the flu vaccine.

If I got a flu shot last year, do I need one again this year?
Yes, you need a flu shot every year.

When should I get vaccinated?
You should get vaccinated as soon as flu vaccine becomes available, but there's still a health benefit in getting a flu shot at any time during the flu season. In the Pacific Northwest, flu activity is usually at its highest level in January or February, and sometimes later. During the 2011-2012 season, we saw very little flu activity until March and April.

Do children need more than one dose of flu vaccine per year?
In general, children under age 9 need two doses of flu vaccine at least four weeks apart during the first year they receive the vaccination. This season, it is recommended that children under age 9 get two flu vaccine doses if they have not received at least two seasonal flu vaccines since July 2010. This is to ensure that young children receive enough of the 2009 influenza A/H1N1 vaccine to offer the best protection.

Are there side effects to the vaccine?
Yes, but most people usually do not have any side effects. When they do happen, side effects are usually mild. The most common side effects are soreness, redness, tenderness or swelling where the shot is given. The flu vaccine cannot give you the flu.

How effective is the flu vaccine?
The effectiveness of the flu vaccine depends on the match between the flu vaccine and the types of flu viruses that are circulating that year. If there is a good match, the flu vaccine is 70-90 percent effective in healthy adults. Flu vaccine is generally somewhat less effective in elderly persons and very young children, but vaccination can still prevent serious complications from the flu.

What are the different types of flu vaccine?
Currently, two types of flu vaccine exist:

  • The flu shot (also call inactivated flu vaccine)
    • Made up of killed viruses
    • Cannot give you the flu
    • Should be given to children 6 months to age 2, people age 50 years and older, pregnant women, and anyone with any health problems or chronic conditions such as diabetes or asthma
  • Nasal spray vaccine (also called live-attenuated influenza vaccine (LAIV) trade name FluMist)
    • Made of live flu viruses that have been changed and weakened (attenuated), so it cannot give healthy people the flu
    • For healthy children and non-pregnant adults between the ages of 2 and 49 only
    • Children and adults with any chronic conditions, including asthma and diabetes, should not receive the nasal spray vaccine
    • Should not be given to household contacts or caregivers of people who are severely immune compromised and have to be in a protected environment (for example, people who have had bone marrow transplant and have to be in the hospital in strict isolation).

Is the flu vaccination safe?
Yes, the flu vaccination is very safe. The Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) hold vaccines to the highest safety standards. Flu vaccines have been given to hundreds of millions of people and have been made the same way for decades.

  • As with all vaccines, flu vaccine testing and safety monitoring are done in multiple phases.
  • For vaccines to be approved, the manufacturing facilities and processes must meet standards to make sure that the vaccines are pure and effective.
  • After vaccines are approved, each batch is tested before it is released to check purity and strength. Several systems are in place to watch for possible side effects after vaccines are given.

Is the nasal spray vaccine safe?
Yes. The nasal spray flu vaccine has been offered for more than nine years and can protect healthy people ages 2 through 49 years from the flu. The nasal spray vaccine cannot give you the flu. It is made from weakened flu viruses that can only infect the nasal passages, not the lungs. Most people don't have any side effects. When people do have side effects, they tend to be mild, for example, runny nose, cough, or nasal congestion. Pregnant women or people with chronic medical conditions, including diabetes or asthma, should not receive the nasal spray. Also children 2-4 yeras old with a history of wheezing should not get the nasal spray; they might have asthma that has not yet been diagnosed.

Is there anything new about flu vaccine and egg allergy?
Yes. People who have severe allergy to eggs should not get a flu shot because the flu vaccine is grown in eggs. This season, CDC has made the guidance clear:

  • If you can eat scrambled eggs without a reaction, you can get a flu vaccination, either a shot or nasal spray.
  • If you get hives after eating eggs, you can get a flu shot (not the nasal spray) and you should be observed for at least 30 minutes to make sure you will not have a more serious allergic reaction.
  • If you have ever had respiratory or cardiovascular symptoms after eating eggs or have ever received medical treatment for an egg allergy, you should see a medical provider who treats allergic conditions.

Is there a special type of vaccine available for seniors?
Yes. Fluzone High-Dose (sanofi-Pasteur) was introduced last year for people age 65 years or older. This vaccine is four times the strength of the regular flu vaccine. Blood tests done for the clinical trials of this new vaccine showed that people who got Fluzone High-Dose had higher levels of antibody in their blood compared with people who got regular Fluzone flu vaccine. It is not yet known whether Fluzone High-Dose will prevent influenza better than regular flu vaccine in people age 65 or older. Studies including up to 33,000 seniors are ongoing and in a few years, these studies will provide more information about the effectiveness of this new vaccine. The Centers for Disease Control and Prevention (CDC) does not specifically recommend the Fluzone High-Dose vaccine for seniors at this time. All people over age 65 should get a flu shot with any of the currently licensed flu vaccines, including Fluzone High-Dose. For more information, see Fluzone High-Dose Seasonal Influenza Vaccine Questions & Answers on the CDC website.

Are there other products available?
A new product called Fluzone Intradermal is a shot that is injected into the skin instead of the muscle. The intradermal shot uses a much smaller needle than the regular flu shot, and it requires less antigen to be as effective as the regular flu shot. It is recommended for adults 18-64 years of age. It usually causes more skin irritation than the regular flu shot, but there is no deep muscle soreness as there sometimes is with the regular flu shot.

Is there mercury in the flu vaccine?
Most flu vaccines contain thimerosal, which is a preservative that protects vaccines against contamination with germs. Thimerosal does contain ethyl mercury in very small amounts. There is no medical evidence of harm caused by the low doses of thimerosal in vaccines, except for minor reactions like redness and swelling at the injection site.

Thimerosal preservative-free flu vaccines are available, but are usually given to children under age 3 and pregnant women. Flu vaccines are available with and without thimerosal. Both options are safe for protecting you and your family from flu. Neither the nasal spray flu vaccine or the intredermal flu vaccine contain thimerosal or other preservatives.

Does the flu vaccine cause Guillain-Barre syndrome?
In 1976, a type of influenza (swine flu) vaccine was associated with Guillain-Barre Syndrome (GBS). Since then, flu vaccines have not been clearly linked to GBS.

GBS is a rare problem in which a person's own immune system damages the nerves, causing muscle weakness and sometimes paralysis. If there is a risk of GBS from current flu vaccines, it would be no more than one or two cases per million people vaccinated. This is much lower than the risk of severe influenza, which vaccination can prevent. Influenza infetion can also lead to GBS.

While is is not fully known what causes GBS, it is known that about two-thirds of people who get GBS do so several days or weeks after they have been sick with diarrhea or a lung or sinus illness.

For more information about flu and flu vaccines, see:

Where to get a flu shot

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