Flu shots are supposed to prevent discomfort and long, restless nights. But, following our October 2008 Web-exclusive "It's Flu Shot Season" story, several of our Web site readers posted comments to our site pointing to their recent flu shots as the possible cause behind mysterious rashes and stomach illness.
Most medical practitioners agree that if you experience sickness or irritation (other than at the site of injection), it’s probably not from the vaccine after all. Nonetheless, if you are breaking out in unusual hives or experiencing soreness, you should talk to your doctor about possible allergic reaction to flu vaccine components including egg and mercury, says UCI Medical Director Susan Haung. Even if you haven’t had such symptoms in the past, your body’s antibodies (developed to fight the flu virus) most likely kicked into overdrive this year and caused a hive reaction. Haung says if you’re experiencing flu-like symptoms after your yearly shot, you most likely caught the virus prior to obtaining the vaccine.
We had more questions for Haung and Linda Dickey, UCI assistant director of Epidemiology and Infection Prevention, about the flu shot and possibility for adverse reactions. Here's what they had to say:
What's a typical flu shot reaction?
LD: Usually responses to the flu vaccine are mild. Most typical are soreness, redness or slight swelling at the injection site, but can also include a low(-grade) fever or aches.
What are symptoms of more severe, negative reactions?
LD: Reactions may include a high fever, difficulty breathing, wheezing, hives, and increased heart rate.
How long do symptoms typically last?
LD: This varies with each person, but will usually occur within minutes to hours after vaccination.
Should someone be concerned if they have any of these symptoms?
LD: Not if the symptoms are mild. But if severe allergic symptoms are noted, or last for an extended period of time, you should contact your doctor right away. If difficulty of breathing occurs, seek immediate medical attention.
What is the solution to these symptoms if not severe?
LD: I would defer to a physician regarding treatment of suspected reactions to the vaccination.
Are symptoms like stomach sickness, diarrhea and hives common reactions to the vaccine?
LD: I have not ever read or heard of diarrhea and stomach sickness being associated with the flu vaccine; hives have been rarely reported, but are usually limited in duration.
Can a flu vaccine actually cause someone to catch the flu or become sick?
LD: Since it contains an inactivated (killed) virus, it cannot cause the flu.
Is there a possibility of a “bad batch” of vaccinations? Has this ever happened?
SH: The flu vaccine is a "custom mix" of viruses each year; scientists watch the virus strains causing illness internationally and use this information to recommend which viruses to put into the upcoming vaccine. The virus is then killed and put into the vaccine to promote immunity to the strains most likely to cause illness. Some years the mix contains a closer match of viruses that end up causing illness than other years. Last year, the vaccine did not cover for one of the virus strains that ended up causing some of the flu cases last year. It was not a bad batch of vaccine as much as a slight mismatch of the viruses it contained with the viruses causing illness. That having been said, the vaccine still provides benefit because it reduces the severity of illness if someone gets vaccinated and still gets the flu with a flu virus strain not covered in the vaccine.