It may be daunting to get a flu shot when you consider the fact that the vaccine is made with weakened pieces of the virus.

Just like with any other vaccine or medical treatment, there are risks and potential side effects of getting inoculated against influenza. But how do those stack up against the risks and side effects of contracting the flu itself? Here’s what you need to know before you decide whether to get the shot this flu season.

Symptoms and side effects

The Centers for Disease Control and Prevention list cold-like symptoms such as fever, sore throat, a cough and a runny or stuffy nose as flu symptoms, as well as muscle or body aches, headaches, fatigue, vomiting and diarrhea.

The flu vaccine, on the other hand, in some cases brings soreness, fainting or swelling from the shot itself, headache, fever, nausea and muscle aches for a couple of days, according to the CDC. People who experience an allergic reaction shortly after receiving the shot could have difficulty breathing, swelling, hives, a fast heartbeat or dizziness, but the CDC says such reactions are rare.

Long-term risks

The CDC notes that some studies have found a rare connection between the flu vaccine and Guillain-Barre syndrome, in which a person’s immune system attacks their nerve cells, causing weakness or even paralysis that can sometimes be permanent. However, other studies have found no connection at all. However, the illness more commonly but still rarely can occur following contraction of the flu, and people can also develop the syndrome completely unrelated to the flu.

In the case of pregnant women, the vaccine could protect a fetus during pregnancy and for several months after birth.

In the longer term, the flu virus can cause pneumonia, as well as serious complications within the muscles and central nervous system, according to the Johns Hopkins Medicine’s health library.


The World Health Organization puts the number of people killed annually by flu at 250,000 to 500,000 — although millions are infected around the globe. However, the WHO also notes that in industrialized countries, like the United States, most flu deaths are senior citizens.

It is more difficult to say specifically how many people die from receiving a flu shot, but the CDC does not mention death under its list of side effects and estimates that severe allergic reactions to the vaccine occur in fewer than one in 1 million doses.

Impact on others

People who contract influenza are contagious even before they know they are sick, in most cases from a day before symptoms begin to develop, according to the CDC. That infectious period continues until five to seven days after the person becomes sick. Additionally, “Some people, especially young children and people with weakened immune systems, might be able to infect others for an even longer time.”

The WHO says the flu spreads easily through contaminated hands. And when someone with the flu coughs, “infected droplets get into the air and another person can breathe them in and be exposed.”

The virus can also hang around on “doorknobs, pens, pencils, keyboards, telephone receivers and eating utensils” even after an infected person has left, according to Johns Hopkins Medicine.