December 7, 2015


Special thanks to The Children’s Hospital of Philadelphia (CHOP) Vaccine Education Center for this guest blog post debunking the myth that influenza (flu) vaccines can give you the flu, as part of the NFID inaugural 2015 National Influenza Immunization Week (NIVW) Blog Relay.

2.1.3-Can-a-flu-vaccine-give-you-the-flu (2).jpgHave you ever spoken with someone who told you that they don’t get the influenza vaccine because it gave them the flu? Is this a reason why you personally don’t get the influenza vaccine for yourself or family members? If so, please read on to learn the facts…

Influenza is often confused with other, more mild respiratory illnesses. But influenza infections are different. First, symptoms of influenza tend to appear suddenly – within a three to six hour window. Second, severe aches, chills, and fatigue tend to be all encompassing and are often accompanied by fever. Finally, respiratory symptoms, such as stuffiness, sore throat, and sneezing, are not typically present, and any cough that occurs tends to by dry and unproductive. People with influenza tend to be fairly ill for two to three days.

None of the influenza vaccines available cause this type of illness, but let’s take a closer look.

Two types of influenza vaccines are commonly available – typically referred to as “the shot” or “the nasal spray.” Neither can cause influenza. Here is why:

  • Shot (injectable) version – The virus strains in the shot have been treated chemically, so they cannot replicate. Without the ability to replicate, a virus cannot cause illness.
  • Nasal spray version – Although this version contains “live” influenza viruses, that is to say, influenza viruses that can replicate, they have been altered in the laboratory. The changes cause them to grow in the relatively cooler nasal passages but not the warmer lung tissues where influenza viruses typically replicate. The result is that protective immune cells are generated, but an infection cannot occur.

Some people experience side effects that might make them think they have an infection, but those side effects are actually the immune system’s response to the vaccine, not symptoms of infection. Common side effects from the shot include redness or pain at the injection site (20%), headache (10%), low-grade fever (10%), or muscle aches (1%). Following the nasal spray version, up to 40% of vaccine recipients may experience runny nose, mild congestion, sore throat, or cough. While these side effects may be uncomfortable, it is important to distinguish them from the miserable, and sometimes severe, symptoms that characterize influenza infection.

Find out more about influenza and the vaccines that prevent it from the Vaccine Education Center (VEC) at CHOP:

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For additional information and resources from CHOP, visit: and

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