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2014-2015 Seasonal Influenza Vaccine Safety

Questions & Answers

What’s in the 2014-2015 seasonal flu vaccine and why?

For the 2014-2015 influenza season, trivalent and quadrivalent inactivated influenza vaccines (IIV) are available. The trivalent IIV is designed to protect against three influenza viruses – one influenza A (H3N2) virus, one influenza A (H1N1) virus, and one influenza B virus. Quadrivalent IIV and live attenuated influenza vaccine (LAIV) contains the same three viruses as the trivalent vaccine, but also contains an additional influenza B virus. For 2014-2015, all doses of the live attenuated influenza vaccine (LAIV), the nasal spray vaccine, are quadrivalent. The availability of particular types of vaccines may vary across health care professionals and health care facilities.

Read more: Prevention and Control of Seasonal Influenza with Vaccines Recommendations of the Advisory Committee on Immunization Practices—United States, 2014-15 Influenza Season

Are the 2014-2015 seasonal flu vaccines safe?

This season’s flu vaccine is expected to have a similar safety profile as past seasonal flu vaccines. Over the years, hundreds of millions of Americans have safely received IIV and LAIV flu vaccines. The most common side effects are soreness, redness, tenderness or swelling where the flu shot was given and nasal congestion after the flu vaccine nasal spray.

Other Vaccines:

  • Flucelvax is the first seasonal influenza vaccine licensed in the United States that is produced using cultured animal cells instead of fertilized chicken eggs.
  • Flublok is the first seasonal influenza vaccine made using recombinant techniques and does not use eggs in its production. Flublok also does not use the influenza virus in its production. The safety profile of these two new vaccines in clinical trials was similar to other IIVs. Common reactions included pain and redness at the injection site, headache, fatigue, muscle aches and malaise. A high dose IIV, called Fluzone High-Dose, contains more antigen than regular IIV and is approved for people aged 65 years and older. Its safety profile is similar to that of regular flu vaccines. During clinical studies, the most common health problems after vaccination were mild and temporary and included pain, redness and swelling at the injection site and headache, muscle aches, fever and malaise. Another kind of IIV, called Fluzone Intradermal, is indicated for adults 18 through 64 years of age and is injected into the skin instead of the muscle. Common reactions to Fluzone Intradermal included redness, swelling, pain, and itching at the injection site. With the exception of pain, these side effects were more common with the intradermal shot than they are with regular flu shots. Other side effects included headache, muscle ache, and tiredness. These symptoms usually go away within 3 to 7 days.

How is the safety of seasonal flu vaccines monitored?

CDC and FDA closely monitor the safety of seasonal influenza vaccine and other vaccines licensed for use in the United States. The purpose of vaccine safety monitoring is to rapidly identify clinically significant adverse events following vaccination. Adverse events, including apparent side effects, following vaccination may be coincidental to (meaning occurring around the same time but not related to vaccination) or caused by vaccination. CDC and its partners use multiple systems to monitor the safety of seasonal flu vaccines. Two of the primary systems that are being used to monitor the safety of these vaccines are the Vaccine Adverse Event Reporting System (VAERS), which is jointly operated with the Food and Drug Administration (FDA), and the Vaccine Safety Datalink (VSD).

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What is the Vaccine Adverse Event Report System (VAERS)?

VAERS is a national program, jointly managed by CDC and FDA, which monitors the safety of all vaccines licensed in the United States. Anyone can file a VAERS report. VAERS relies on information included in these reports to monitor for health problems following vaccination. Healthcare providers are encouraged to report possible adverse events after vaccination, even if they are not certain that the vaccine caused the event. FDA and CDC use VAERS data to help identify adverse events that may be associated with vaccination. Generally, VAERS cannot determine if an adverse event was caused by a vaccine, but it can help determine if further investigations are needed. If safety concerns are identified in VAERS, further investigation is often undertaken. One important system used to further evaluate concerns identified in VAERS is the Vaccine Safety Datalink (VSD) Project. More information about VAERS is available.

What is the Vaccine Safety Datalink (VSD)?

The VSD is a vaccine safety system used to both monitor and assess adverse events following vaccination. VSD is a collaboration between CDC and several integrated healthcare organizations with medical care and vaccination data on approximately 9 million people. During the influenza season, VSD regularly monitors for certain adverse events that could be associated with flu vaccine. VSD conducts studies of vaccine adverse events and health outcomes of concern that may arise with any vaccine.

Are there any side effects to the seasonal flu vaccine?

There are multiple flu vaccine choices this year. Millions of seasonal flu vaccines have been given safely. CDC expects that any serious side effects following vaccination with the 2014-2015 flu vaccine will be very rare. Mild side effects that may occur are expected to be similar to those experienced following past seasonal influenza vaccine.

The flu shot: The viruses in the flu shots are either killed (inactivated) or recombinant (don’t contain virus particles), so you cannot get the flu from a flu shot.

The quadrivalent vaccines’ safety profile in pre-licensure trials have been very similar to the older trivalent flu vaccines.

Most people who receive the flu shot do not experience serious problems from it. Mild problems that may be experienced include soreness, redness, or swelling where the shot was given, fainting (mainly adolescents), headache, muscle aches, fever, and nausea. If these problems occur, they usually begin soon after the shot and last 1 to 2 days. Life-threatening allergic reactions to vaccines are very rare. If they do occur, it is usually within a few minutes to a few hours after the shot is given.

The nasal spray (also called LAIV): The viruses in the nasal-spray vaccine are weakened and do not cause the severe symptoms that are often associated with influenza illness. (Because the nasal spray vaccine uses live – although weakened – virus, it is possible to transmit the vaccine virus to close contacts. This has very rarely occurred in clinical studies. For more information on who should and should not receive the nasal-spray vaccine, please see the LAIV VIS statement or Guidelines for Flu Vaccination, 2014-2015.

This year, all nasal spray contains four attenuated flu viruses. However its safety profile has been very similar to the older flu vaccines in pre-licensure trials.

In children, side effects from LAIV can include:

  • Runny nose
  • Wheezing
  • Headache
  • Vomiting
  • Muscle aches
  • Fever

In adults, side effects from LAIV can include:

  • Runny nose
  • Headache
  • Sore throat
  • Cough
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Are there symptoms that should cause concern after getting a flu vaccination?

Signs of a serious allergic reaction can include difficulty breathing, hoarseness or wheezing, swelling around the eyes or lips, hives, paleness, weakness, a fast heart beat or dizziness. In addition, after vaccination you should look for any unusual condition, such as a high fever or behavior changes. If any unusual condition occurs following vaccination, seek medical attention right away. Tell your doctor what happened, the date and time it happened, and when the vaccination was given. Ask your doctor, nurse, or health department to report a possible reaction by filing a Vaccine Adverse Event Reporting System (VAERS) form. Or you can file this report yourself through the VAERS website. You may call 1-800-822-7967 to receive a copy of the VAERS form. VAERS does not provide medical advice.

There is a small possibility that IIV could be associated with Guillain-Barré Syndrome (GBS), no more than 1 or 2 cases per million people vaccinated. This is much lower than the risk of severe complications from flu, which can be prevented by flu vaccine.

Are there some people who should not receive this vaccine?

People who have had a severe (life-threatening) allergy or reaction to a previous flu vaccine should not be vaccinated. People who have an allergy to eating eggs should discuss flu vaccination with their doctor. Many people who are egg-allergic can safely receive influenza vaccine. See Special Consideration Regarding Egg Allergy for more information.

What is the best source of information for seasonal flu vaccine safety?

In addition to talking openly with your health care provider, CDC encourages you to stay informed by checking the following web sites often for the most up-to-date news and information: Seasonal flu.

CDC and the FDA will closely monitor for any signs that the seasonal flu vaccine is associated with unexpected adverse events and will work with partners to investigate any unusual events.

If you believe you have been injured by a flu vaccine you may be eligible to receive compensation from the federal government for your injuries if certain criteria are met. To learn more visit the National Vaccine Injury Compensation Program website or call 1-800-338-2382.

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