The flu shot and FluMist: side effects, safety, and more

Every year, between 5–20% of the U.S. population catches the flu, and between 12,000 and 61,000 die from it (CDC, 2021). And even though our awareness regarding respiratory viruses, proper hand hygiene, and the importance of vaccines has increased since the start of the coronavirus pandemic, not everyone knows just how important it is to get vaccinated against the flu every year. 

We spoke with Dr. J. Zachary Porterfield, MD, PhD, a physician scientist and specialist in infectious disease and global health, about the importance of getting vaccinated against influenza, common misconceptions about getting the jab, and how it all relates the coronavirus pandemic. 

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The flu shot, or influenza vaccine, is a way to keep you from catching the flu and to decrease how sick you become if you do catch the flu. Vaccines work by giving your body exposure to an inactive or weakened form of an infectious agent. This gives your immune system the ability to fight off that specific infection if you get exposed to it later. Vaccines use your body’s natural defense system and teach it to fight a particular invader before you encounter it.

The flu vaccine is recommended for everyone over the age of six months. The only exceptions to this recommendation are individuals who have a history of severe reaction to the flu vaccine in the past or those who are currently ill. Individuals who are sick should get the flu vaccine once they recover from the illness.

The flu, also known as influenza, is a common and highly contagious infection of the lungs, nose, and throat caused by the influenza virus. It typically causes fever, cough, sore throat, muscle aches, and headache, usually during the winter months. 

The flu is spread from person to person by tiny droplets created when a person coughs, sneezes, or talks. It typically spreads when there is close contact between people or in closed spaces. 

“Most flu infections last 1–2 weeks,” says Porterfield, “and the body usually recovers on its own. Despite being common, many people underestimate the danger of the flu.” 

Each year, up to 40 million people in the United States come down with the flu and in the most serious cases, it can be deadly. Most of these deaths occur in people over the age of 65 or who have other chronic health problems (CDC, 2021). 

But that doesn’t mean you should skip your annual vaccine if you’re young and healthy. Many of the vaccines we take routinely are meant to provide herd immunity to protect the most vulnerable members of our communities. 

When people get vaccinated, they are less likely to catch and transmit the virus to other people, including people who have weakened immune systems and those who are more likely to suffer serious or deadly complications from the virus.

There are treatments for people who have the flu, as well as vaccines to protect you from getting it in the first place. While vaccination is the best way to avoid getting infected, there are additional steps you can take. For example, you can wash your hands often, avoid touching your eyes, nose, and mouth, limit your contact with people who are sick, stay home if you have flu symptoms, and cough or sneeze into a tissue rather than your hands.

When you get vaccinated against the flu, it not only decreases your chance of catching the flu, but it also reduces how sick you get if you do catch the flu.

The flu vaccine is available in two forms: as a shot that is injected into your arm and as an inhalable mist (also known as Flumist). The shot itself takes just a few seconds and can be a bit uncomfortable, but the discomfort passes quickly. Some people report pain in their arm at the site of the injection for about 24 hours after they get their shot. 

The most common side effect of the flu vaccine is soreness at the site of the injection. Occasionally, the flu vaccine can cause fever. In exceptionally rare cases (about 1 case per million vaccines given), it is associated with a problem with the nervous system called Guillain-Barré syndrome. The flu vaccine is recommended for everyone because the benefits of vaccination greatly outweigh the risk of side effects.

FluMist is a specific type of flu vaccine. It’s what is called a live attenuated influenza vaccine (LAIV) which is used to prevent the flu in people ages 2–49 who are not pregnant. The FluMist vaccine is administered using a small, needleless syringe, and inhaled in the nose. While this vaccine is less uncomfortable than getting a shot, it isn’t available every year. That’s because the vaccine was found to be less effective against certain forms of the flu virus that were circulating in particular years (Grohskopf, 2018). 

Side effects are typically mild and are similar to the side effects from the flu shot. They can include (CDC, n.d.): 

• Runny nose

• Headache

• Cough

There is quite a bit of misinformation regarding the flu and the flu vaccine. Some of the more common ones include:

Myth: Getting the flu shot gives you the flu.

Fact: Some people have mild side effects from the flu vaccine, and, rarely, one side effect can be fever. These symptoms are not the flu. Instead, any symptoms you experience after getting the vaccine are due to your immune system building up a defense against the flu.

Myth: Healthy people do not need to get vaccinated.

Fact: The flu vaccine is recommended for everyone older than six months of age, with very few exceptions. The flu can infect young, healthy people and cause severe illness and even death. Getting vaccinated also helps protect people who may not be able to get vaccinated themselves. The more vaccinated people in the community, the harder it is for the flu to spread.

Myth: Pregnant women cannot get the flu shot.

Fact: Pregnant women are at increased risk of getting severely ill from the flu and are one of the key groups to be vaccinated.

Influenza virus is different from the novel coronavirus, which causes COVID-19—but they have some similarities. Many viruses, including the novel coronavirus, can cause symptoms similar to the flu, including fever and cough.

There are treatments and vaccines for the flu, as well as widely available vaccines for the prevention of COVID-19. Treatment options for people already infected with COVID-19 are limited, but most cases resolve on their own with supportive care.

In October of 2020, the FDA approved Remdesivir, an antiviral medication, for the treatment of COVID-19 (FDA, 2020). The medication was shown to improve symptoms and shorten hospital stays in comparison to placebo in patients hospitalized with coronavirus (Beigel, 2020). Since then, other treatments have also shown promising results in trials, including fluvoxamine, an antidepressant medication. 

There are treatments that can shorten the duration of the flu, too, such as oseltamivir (also known as Tamiflu) and techniques used to prevent transmission. These precautions (such as hand washing and staying home if you're sick) help prevent transmission of the novel coronavirus, too. 

Luckily, there are vaccines available for both coronavirus and the flu. Getting vaccinated can prevent you from catching these diseases and protect the people around you. Given the strain on the healthcare system from COVID-19, it is important to do all that we can to decrease infections from other sources, including the flu.

When you get vaccinated against the flu, it not only decreases your chance of catching the flu, it also decreases how sick you get if you do catch the flu. Getting your flu shot also helps protect people around you from getting sick. This is especially true for people at high risk of serious illness from the flu, including people over 65, children, pregnant women, and people with weakened immune systems or chronic diseases. When most people in a community get vaccinated against a disease, the disease cannot spread easily. Make sure to stay up to date on local guidelines regarding vaccinations and booster shots and get your annual flu vaccination. 

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Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

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Current version

September 11, 2021

Written by

Zachary Porterfield, MD, PhD

Fact checked by

Yael Cooperman, MD

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About the medical reviewer

Yael Cooperman, MD, Ro

Yael Cooperman is a physician and works as a Senior Manager, Medical Content & Education at Ro.