Can a Flu Shot Give You the Flu?

1 answer | Last updated: Jan 24, 2013
A fellow caregiver asked...

Can a flu shot give you the flu?

Expert Answers

Dr. Leslie Kernisan is a senior medical editor at and a clinical instructor in the University of California, San Francisco, Division of Geriatrics. She also provides housecalls and geriatric consultations in San Francisco.

No. Since the flu shot contains killed virus, it's not possible to get influenza from this vaccination. The less commonly used nasal vaccine (also known as FluMist) does use a live but very weak virus. Although it's theoretically possible that someone could get influenza from the nasal vaccine, this has not been seen in the big trials that studied it in healthy adults up to 49 years of age.

Both vaccine types contain traces of chicken eggs, which can be a problem for those with egg allergies.

It's not uncommon to notice some mild side effects in the days after you get a flu shot, but experts unanimously agree that the benefits of vaccination vastly outweigh the risks. Remember that, on average, every year 36,000 Americans die from seasonal influenza.

The flu shot can cause a sore arm, and it sometimes causes mild fever and achiness that can feel like a mild case of flu to some people. The nasal vaccine has been linked to symptoms such as runny nose, cough, and sore throat. Currently, only the flu shot is recommended for adults older than 50. Those younger than 50 should talk to a doctor to help decide which form of vaccination makes the most sense.

By the way, whether you choose the flu shot or the nasal vaccine, all flu vaccines for the fall of 2010 include protection against the H1N1 influenza virus (also known as the "swine flu"), so there should be no need for a separate vaccination for H1N1.