A yearly flu vaccine is the protection against the flu. How well does it work? Studies by CDC researchers and other experts indicate the flu vaccine reduces the risk of doctor’s visits due to flu by about 40-60%.1 Although it does not guarantee complete protection against the flu, people who get the vaccine are less likely to get sick.2

What is a flu vaccine?


Influenza vaccines are developed twice a year, as the influenza virus changes rapidly. Scientists identify new flu strains and determine which strains of the virus are most likely to spread and cause illness in the upcoming flu season.3 They meet in February to determine the recommended composition for the yearly flu vaccine to be produced in the northern hemisphere; they meet again in September to make the same decision for the southern hemisphere.

The most common way flu vaccines are made is using an egg-based manufacturing process. It is used to make both inactivated (killed) virus vaccines (the flu shot) and live (weakened) virus vaccines (the nasal spray).3 This egg-based production process begins with candidate vaccine viruses (CVVs) grown in eggs. These viruses are then injected into fertilized hens’ eggs and incubated for several days to allow the viruses to replicate. The virus fluid is then harvested from the eggs.

To create the flu shot, the flu viruses are inactivated (killed), and the virus antigen is purified. It is then further purified and tested. For the nasal spray vaccine, the CVVs are weakened and then go through a different production process. The FDA tests and approves all vaccines prior to their release.

Can a flu shot give you the flu?

No, the flu shot cannot cause flu illness. The vaccine is made with either a) flu virus that has been inactivated and is not infectious or b) no flu viruses at all.1 The most common side effects from the shot are soreness, redness, and tenderness at the site of the shot.

Do I really need a flu vaccine every year?

Yes. The CDC recommends a yearly flu vaccine for just about everyone 6 months and older, even when the viruses the vaccine protects against have not changed from the previous season.1 This is because a person’s immune protection from vaccination declines over time, so an annual vaccination is needed to get the optimal protection against the flu.

Why did I still get sick after getting the flu vaccine?

There are several reasons this could have happened:

-          People can become ill from other respiratory viruses that cause symptoms similar to the flu; the flu vaccine only protects against influenza.

-          It is possible to be exposed to the flu shortly before getting vaccinated or during the two-week period after the vaccination that it takes the body to develop immune protection.1

-          You could have been exposed to a flu virus that is very different from the viruses the vaccine protects against. There must be a “match” between the viruses selected to make the vaccine and those spreading and causing illness.

-          The flu vaccine can vary in how well it works, and some people who get vaccinated may still get sick.

The Campus Health Center (CHC) offers all currently enrolled WSU students flu shots at no out-of-pocket charge. If insurance does not cover a WSU student’s flu shot or if a student does not have insurance, they will not receive a bill.

Check the Campus Health Center website for dates and locations of flu vaccination events:


Help WSU win the National College Flu Vaccination Challenge by completing this 30-second survey: https://s.surveyplanet.com/S1ewWDYZqG


  1. “Influenza (Flu).” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 25 Sept. 2018, www.cdc.gov/flu/about/qa/misconceptions.htm.
  2. “Why Get a Flu Vaccine.” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 1 Oct. 2018, www.cdc.gov/flu/pdf/freeresources/general/strong-defense-against-flu.pdf.
  3. Stierwalt, Sabrina. “How Are Seasonal Flu Vaccines Made?” Scientific American, 4 Feb. 2016, www.scientificamerican.com/article/how-are-seasonal-flu-vaccines-made/.

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