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2012-2013 Seasonal Influenza Vaccine Safety

Questions & Answers

What’s in the 2012-2013 seasonal flu vaccine and why?

The 2012-2013 seasonal influenza vaccine protects against three influenza viruses – one influenza A (H3N2) virus, one influenza A (H1N1) virus, and one influenza B virus. The H1N1 virus the 2012-2013 seasonal flu vaccine protects against is the 2009 H1N1 influenza virus because scientists expect to continue to see this virus circulate in the United States.

Are the 2012-2013 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 seasonal 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.

A new high-dose seasonal flu vaccine (Fluzone High-Dose) was introduced during 2010-2011 for adults 65 and older to stimulate a stronger immune response (more antibody) in the person getting the vaccine. Another new vaccine, Fluzone Intradermal, was also licensed for use in the United States in 2011-2012. The vaccine is injected into the skin instead of the muscle and requires a smaller dose than the regular flu shot. It is recommended for adults 18-64 years of age. Both the high dose and intradermal vaccines are available for the 2012-2013 influenza season.

The safety profile of Fluzone High-Dose 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. Most people had minimal or no adverse events after receiving the Fluzone High-Dose vaccine.

In studies for Fluzone Intradermal, common reactions to the shot included redness, swelling, toughness, 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 immunization. Adverse events, including apparent side effects, following immunization 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 this season’s 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).

Vaccine Adverse Event Report System (VAERS)

VAERS is a national program that is jointly managed by CDC and FDA to monitor 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 that follow vaccination. Health care providers are encouraged to report possible adverse events after immunization, even if they are not certain that the vaccine caused the event. Generally, VAERS cannot determine if an adverse event was caused by a vaccine, but it can help determine if further investigations are needed. FDA and CDC use VAERS data to help identify adverse events that may be associated with vaccination. If safety concerns are identified in VAERS, further investigation is often needed. One important system used to further evaluate concerns identified in VAERS is the Vaccine Safety Datalink (VSD) Project. More information about VAERS is available.

Vaccine Safety Datalink (VSD)

The VSD is a vaccine safety system used to both monitor and assess adverse events following immunization. VSD is a collaboration between CDC and 10 large managed care organizations, in which comprehensive medical information is collected on approximately 9 million people. During the influenza season, VSD regularly monitors data 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?

A list of possible side effects from both the flu shot and the nasal spray (referred to as LAIV or Flu Mist) vaccines are below:

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
  • Nausea

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.

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, particularly those who have weakened immune systems. This has rarely occurred in clinical studies. Therefore, the nasal spray vaccine should not be given to people in close contact with someone whose immune system is so weak they require care in a protected environment. For more information, see the LAIV VIS statement [274 KB, 2 pages].

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

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 1-2 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.

This season’s flu vaccine is made the same way as past seasonal flu vaccines. Millions of seasonal flu vaccines have been given safely. CDC expects that any side effects following vaccination with the 2012-2013 flu vaccine would be rare. Any side effects that may occur are expected to be similar to those experienced following past seasonal influenza vaccine.

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.

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 egg-allergic individuals can safely receive influenza vaccine.

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, and Flu.gov.

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 at http://www.hrsa.gov/vaccinecompensation/index.html or call 1-800-338-2382.

Last syndicated: January 15, 2014
This content is brought to you by: Centers for Disease Control and Prevention (CDC)