The Side Effects Of The Flu Shot Are Typically Greatly Exaggerated
Ahh, flu season. It happens every year. Influenza, commonly referred to as the flu, is a serious disease caused by influenza viruses. In some cases, the flu can lead to hospitalization and worse, death. The best way to protect yourself is by getting vaccinated. As important as that is, it's totally reasonable to worry about potential flu shot side effects.
First, know that the vaccine works really well, with various estimates showing its effectiveness in reducing the risk of life-threatening disease somewhere in the range of 40 to 60 percent, and as high as 75 percent among children.
Worried about catching the flu from getting jabbed? Rest assured, it is not possible to contract influenza from the vaccine, says Michael Hanak, MD, the associate chief medical officer for Population Health. “The vaccine is made from inactivated viral particles, which do not cause illness."
That said, many people do experience mild flu-like symptoms after vaccination, which is a sign that your body is producing antibodies and generating an immune response. And that's a good thing!
Flu viruses typically spread in fall and winter, peaking between December and February, according to the FDA. Every flu season is different, and the health impact vary widely from year to year. Because of that, the flu vaccine is updated every year to protect against new flu virus strains that are expected to circulate and cause illnesses.
Meet the experts: Amesh A. Adalja, MD, is an infectious disease physician and a senior scholar at Johns Hopkins University for Health Security. His work is focused on emerging infectious disease, pandemic preparedness, and biosecurity.
Michael Hanak, MD, is a family medicine physician and an associate professor in the department of family & preventive medicine at Rush Medical College.
Soma Mandal, MD, is an internist at Summit Medical Group in Berkeley Heights, New Jersey.
It's more important than ever to get vaccinated this year.
We are in the midst of a significant and early uptick in cases and severity, says Dr. Hanak. “The CDC reported the most flu-related hospitalizations at this point in the year since the pandemic, with an estimated 880,000 cases of flu nationwide,” he notes. Influenza is responsible for thousands of hospitalizations and hundreds of deaths each year, and while the flu vaccine does not protect 100 percent of people from actually contracting the flu, much like the COVID vaccine, it can prevent severe illness.
And side effects are transient and typically last one to two days after vaccination, says Sindhu Aderson, MD, the medical director of Northwestern Medicine Immediate Care. People who are vaccinated and get sick anyway tend to experience less severe symptoms as well as decrease their risk of hospitalization. “This is why the flu shot is an incredibly important tool to keep ourselves and those around us safe,” she says.
If you are thinking of getting a flu shot this year, plan accordingly. The vaccine can take 14 days to take full effect, according to Dr. Hanak, so take into account any holiday plans or upcoming travel.
Since the vaccine is not immediately effective, many people who receive the vaccine but shortly before or after being exposed to influenza or another virus (i.e., a cold) will become ill from that. And that's completely unrelated to their vaccination.
Another thing to note? Talk of the flu shot’s many side effects is greatly exaggerated. The flu shot can’t actually give you the flu, and while there are some possible side effects, infectious disease expert Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security, says most are rare.
If you’re particularly wary of needles, you may prefer the nasal influenza spray (Flumist) over an injection, says Soma Mandal, MD, an internist at Summit Medical Group in Berkeley Heights, New Jersey. Potential nasal spray side effects include runny nose, wheezing, headache, vomiting, muscle aches, fever, sore throat, and cough.
“Not everyone should get the nasal flu spray due to factors like age and underlying health conditions, though, so talk to your doctor to determine if it’s the best option for you,” she says.
The flu shot is still worth it despite potential side effects.
Here are the flu shot side effects to be aware of this season, from common soreness and redness to rare effects like Guillain-Barre syndrome. After you've read through them, roll up your sleeve because flu season is coming. And guess what? The vaccine is still your best stay-healthy defense.
1. Shoulder soreness
If you receive the flu shot as an intramuscular injection (a.k.a. in your arm, typically), you have a 10 to 64 percent chance of experiencing some muscle soreness in your upper arm, according to the CDC.
That’s because the needle is injected directly into the muscle, causing microscopic damage to the cells, and is designed to cause an inflammatory immune system response. You can take an OTC pain reliever while you wait for the soreness to fade, but if the pain is very noticeable or decreasing your mobility, Dr. Adalja recommends checking with your doctor.
What to do: If you are experiencing shoulder soreness, especially at the injection site, Dr. Hanak recommends taking Tylenol. “I generally recommend using Tylenol to address post-vaccine symptoms, as other anti-inflammatory medications can potentially interfere with the vaccine and immune response process.”
2. Redness or swelling at the injection site
Anytime you pierce the skin and put something into the body it can cause a topical reaction, says Dr. Adalja. This is just a sign that your immune system is activating.
But this redness and swelling where you get your shot is a common side effect that only typically lasts a few days. It’ll go away on its own, but if it’s really bugging you, you can take ibuprofen (Advil) or acetominophen (Tylenol).
What to do: You can use topical creams to mitigate any redness or swelling, says Dr. Hanak. He also advises avoiding activities involving the shoulder and to take Tylenol as needed. You may even want to schedule your flu vaccine before a weekend or a day off from the gym to avoid having to use your arm, which may be sore post-vaccination.
3. Body aches
Any vaccine can cause body aches because of the way in which they activate the immune system, says Dr. Adalja.
If you’re feeling sore in places other than your arm, it's usually nothing to worry about, though Dr. Adalja notes that the flu shot does take two weeks to become fully effective—so your body aches could be a sign of the actual flu, since viral strains are probably circulating around the time you get the vaccine.
What to do: Hydrate with plenty of water and to take Tylenol is your best bet at relieving body aches.
4. Itching at the injection site or a full-body rash
This would signal an allergic reaction, but “it’s very rare to have an allergic reaction to the flu shot,” Dr. Adalja notes. “There are lots of myths about egg allergies and the vaccine," he explains—because most flu shots and nasal sprays are manufactured using technology that involves small amounts of egg proteins, per the CDC.
"If you can eat scrambled eggs, you’re not going to have a problem with the flu shot,” Dr. Adalja says. If you have a confirmed egg allergy, you can likely still get the shot, the CDC says.
The caveat: If you experience severe itching at injection site, a rash all over your body, or signs of anaphylactic shock, seek immediate medical attention. And if you’ve had an allergic reaction to the flu shot in the past, you are among those few groups of people who the CDC recommends skip the flu shot.
What to do: Dr. Hanak recommends taking an allergy medication like Benadryl or using any anti-itch creams or lotions like a topical Benadryl cream to help with the discomfort.
5. Fever
You probably won’t get a fever because of the vaccine, but if you do, it should be low-grade (i.e. less than 101 degrees). If it’s higher than that, don’t blame your flu shot—you probably have a totally unrelated illness. “Remember that you’re getting the vaccine at the height of respiratory virus season,” says Dr. Adalja. “So you may have been incubating another virus [without knowing it].”
And once again (for the people in the back!): The flu shot cannot give you the flu. While some flu vaccines contain virus strains, they're not live strains, so they can’t get you sick. Meanwhile some flu shots don’t contain the virus at all (they only contain a specific protein from the influenza virus), per the CDC.
What to do: Drink cold fluids, stay hydrated, and take Tylenol until the fever subsides, says Dr. Hanak.
6. Dizziness or fainting
This is less a side effect of the vaccine itself and more a side effect of a needle phobia, says Dr. Adalja. If you think you might have a stress reaction or faint, give your health care provider a heads up so they can make sure you stay seated after the shot to prevent injury.
What to do: Dr. Hanak advises monitoring your blood pressure and reporting to your doctor. You will also want to stay hydrated.
7. Headache
An aching head is included in the CDC’s official list of potential side effects, but Dr. Adalja says it’s nbd. “It is just part of the immune reaction to the vaccine,” he says, adding that it usually goes away pretty quickly and can “easily” be treated with acetaminophen (aka Tylenol). FWIW: Some of the headaches could just be due to anxiety about getting a shot, Dr. Piedra says. “People could receive a placebo shot and get headaches as well,” he says.
What to do: Drink plenty of fluids and take some Tylenol until your headache subsides.
8. Nausea
This is another one listed by the CDC that Dr. Piedra says is likely due to anxiety. “There are people that, when they get an injection of whatever type, can have some gastrointestinal manifestations afterward, including nausea,” he says. “It’s often attributed to anxiety.” It’s possible to have a little nausea as a larger part of your body’s response to the flu vaccine, Dr. Adalja says, but it doesn’t last long. Dr. Piedra agrees: “It will flee rapidly.”
What to do: Take some supplements or OTC meds to tame your stomach, such as B6 supplements, Dramamine, ginger supplements, and Pepto-Bismo. You may even want to make some dietary changes depending on what types of beverages and foods your stomach can handle.
9. Guillain-Barre syndrome
Guillain-Barre syndrome (GBS) is an auto-immune disorder that’s triggered by a wide variety of things, from vaccines to viral infections.
GBS causes damage to the nervous system, resulting in symptoms like muscle weakness, numbness, difficulty walking or an odd gait, and even paralysis, says Dr. Adalja. While 70 percent of people fully recover from the disorder, the recovery period can range from weeks to even years, according to the National Institute of Neurological Disorders and Stroke.
But he also says the connection between GBS and the flu vaccine has been overhyped: “People should remember that influenza itself is much more likely to cause GBS than the vaccine.”
And since no more than one or two cases per million people vaccinated will have this side effect, it’s better to take your (super small) chances with GBS than with one of the many common, severe complications that often come with the flu itself.
What to do: Studies have shown that the likelihood of contracting GBS is actually higher after having influenza than after receiving the influenza vaccine, notes Dr. Hanak. “On average we see one to two cases per million vaccinations, but the evidence is not clear yet as to how strong a link exists.” For example, a recent study published in JAMA reported that 13 million older adults showed no increase in GBS following flu vaccination. If you experience any of the symptoms of GBS, it's best to check in with your doc about next steps.
10. Severe allergic reaction
Any medication or vaccination has the potential for adverse effects including severe life-threatening reactions, says Dr. Mandal. Severe allergic reactions typically occur within a few hours of receiving the vaccine. These include hives, wheezing, shortness of breath, fast heart rate and dizziness.
“It is important to seek immediate medical attention if you develop any of these symptoms,” she says. It's definitely scary, but know that this side effect is super rare.
What to do: Take an allergy medication, such as Benadryl, and contact your primary care physician. In some instances, you may even need to go to a clinic or emergency room for steroids or other treatments to help quell these flu shot side effects if they are severe.
11. Fatigue
Another flu shot side effect is fatigue and a runny nose, notes Dr. Hanak. “These are usually short-lived symptoms anyhow,” he says.
What to do: If the side effects are bothersome, drink plenty of fluids, rest, and use nasal decongestants for nasal symptoms.
Why do some people get side effects and others don’t?
It is estimated that up to 20 percent of people with influenza do not exhibit symptoms, which further shows everyone needs to get vaccinated, explains Dr. Hanak. “Similarly, varying levels of immune response occur with the flu vaccine, which can produce a wide variety of symptoms, including none at all,” he says.
Many factors can play a role, including age, medications taken regularly, other health conditions, and timing (i.e., receiving the shot when you have seasonal allergies or other ongoing illnesses).
The flu vaccine is designed to stimulate your immune system to build antibodies against the virus, and the thought here is that those people having side effects from the flu shot are those whose bodies are having a robust response to the vaccine, says Dr. Aderson.
As with many things in life, everybody and every body will respond differently to the flu shot depending on many different factors.
The bottom line: For most everyone, the flu shot is safe and only causes mild symptoms that are pretty much just annoying. The benefits of not getting the flu (and not spreading it to others who may be more vulnerable to the illness) far outweigh the risks of getting the shot.
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