Flu Vaccine Myths

There are many myths surrounding flu vaccines. This page will help you to sort through some of the statements you may have heard from friends, family, or social media.

Myth #1: The flu shot gave me the flu.

Flu shots do not have any live influenza virus in them, and therefore cannot give you the flu. The vaccine contains a protein that lives on the surface of the influenza virus. Your immune system makes antibodies to this protein after you get vaccinated. With these antibodies your body is ready to fight the actual virus. Sometimes flu shots cause muscle soreness that can mimic the muscle aches of influenza, or cause a fever. However, the flu shot does not cause the influenza syndrome that includes fever, muscles aches, runny nose, congestion, cough, sore throat, headaches, nausea and/or vomiting.

Because most individuals get their flu vaccine during (not before) flu season, there is a constant risk of exposure to influenza just before getting the vaccine. The timing of symptom onset relative to getting the shot makes it hard for patients to ignore. They incorrectly assume the flu shot caused the symptoms, when really they got the flu before the flu vaccine had a chance to become protective.

Flumist is what is called a live attenuated virus vaccine and is administered by nose spray. This means there is actual influenza virus in the vaccine, but it has been weakened enough to not cause the illness itself. Enough of the virus is present however to create an immune system response. Like the flu shot, Flumist does not cause full influenza syndrome. That said, about 7% of children develop fever in response to Flumist and about one third develop runny nose or congestion.

Myth #2: The flu shot doesn’t work.

We all wish the flu vaccine was 100% effective. Influenza is a very adaptable virus, and is constantly changing its clothes, so to speak. Our immune systems therefore have a hard time recognizing it from year to year. Furthermore, scientists have a very challenging job to anticipate which strains of influenza are going to circulate in a given flu season. The fact that protection is as high as 60% in some seasons is a testament to the hard work and research done year-round by these scientists.

Yes, it’s true, people may get the flu even if they had the vaccine. However, their course of illness is generally more mild than it would have been had they not had the vaccine. This means fewer complications, hospitalizations, and deaths due to the flu. Getting the flu despite receiving the vaccine doesn’t mean the vaccine doesn’t work, it just means it doesn’t work as well as we’d like – we can all agree on that. That said, it’s the best we have, and any protection is better than no protection.

Myth #3: I got the flu already this season, so I don’t need a flu shot.

This theory makes some sense. If your child has had chicken pox, for example, he or she does not need to get the chicken pox vaccine. But there’s only one strain of Varicella – the virus that causes chicken pox. In a given flu season, however, multiple strains circulate. And those strains change from flu season to flu season. Most flu vaccines (including the one we offer to our patients) provide protection against 4 strains of influenza. Typically 2 of those strains are “A” strains and 2 are “B” strains. Getting a flu vaccine the week after you recover would still help protect you against the 3 other strains for the rest of the flu season.

Myth #4: I am – or, my child is – healthy so I can just rely on my immune system to fight the flu if I get it. Therefore I don’t need the vaccine.

While most healthy individuals who get the flu have a self-limited illness from which they recover just fine, that is not always the case. The young (<2), the old (>65), those with weakened immune systems due to illness or medications, and those with heart or lung conditions are at the highest risk for complications from the flu. However, for the 2018-19 flu season approximately 45% of children hospitalized, and 49% of children who died due to influenza had no underlying medical conditions***.

Vaccinating yourselves and your children provides some “herd immunity” to protect high-risk individuals who can’t get the vaccine (e.g. newborns and infants < 6 months). It also decreases spread of the flu, which lowers the likelihood of both healthy & high-risk individuals getting sick.

*** https://www.cdc.gov/mmwr/volumes/68/wr/pdfs/mm6824a3-H.pdf