7 Most Common Flu Shot Side Effects

WRITTEN BY: Craig Sturgill


The flu shot plays a crucial role in preventing seasonal influenza outbreaks. Administered annually, it safeguards individuals and communities alike. However, some recipients experience common side effects, raising concerns for many.

What is the flu shot?

The flu shot is a vaccine designed to protect against the influenza virus. Developed annually, it targets the most prevalent flu strains. Once administered, the vaccine introduces inactivated or weakened flu viruses into your body. This prompts your immune system to produce antibodies. When exposed to the actual virus later, your body recognizes and combats it swiftly to prevent you from getting a really bad case of the flu.

Who should get the flu shot?

The flu shot is recommended for a broad spectrum of the population to ensure both individual and community protection. The vaccine benefits everyone, but certain groups should get vaccinated due to their heightened risk of complications or exposure.

  • Children aged 6 months and older
  • Anyone over age 65
  • Pregnant women, to protect both mother and baby
  • Healthcare workers who are frequently exposed to the virus
  • People with chronic medical conditions such as asthma, diabetes, or heart disease

Herd immunity plays a pivotal role in flu prevention. When a significant portion of a community gets vaccinated, the spread of the virus slows down, offering protection even to those who haven’t been vaccinated. This helps safeguard the most vulnerable parts of the population.

When should you get the flu shot?

The optimal time to receive the flu shot is early fall, before flu season peaks. By getting vaccinated then, you allow your body ample time to develop immunity. However, getting the shot later can still offer protection.

Vaccination frequency is crucial. The flu virus mutates over time, and new strains emerge annually. Therefore, yearly vaccinations are recommended to ensure continued protection.

Common flu shot side effects

While the flu shot is generally safe, some recipients might experience side effects. These reactions, typically mild, vary among individuals.

1. Soreness at the injection site

After receiving the flu shot, many individuals experience soreness at the injection site. This mild discomfort typically lasts a day or two. Applying a cold compress can often alleviate the pain.

2. Mild fever

A mild fever can sometimes follow the flu shot. This is a sign that the body is building immunity. Typically, it subsides within 24 to 48 hours.

3. Fatigue

Fatigue post-vaccination results from the body’s immune response being activated. It’s a common side effect, indicating the vaccine is working. Most people recover from this tiredness within a day or two.

4. Headache

The body’s immune response can often cause headaches after the flu shot. While usually mild, they can be bothersome. Over-the-counter pain relievers and rest typically alleviate the discomfort.

5. Muscle aches

Muscle aches can manifest after the flu shot, reflecting the body’s immune activity. These aches are generally mild and short-lived. Warm compresses and gentle stretches often provide relief.

6. Nausea

The flu vaccine can cause nausea as a rare side effect, which is thought to be linked to the body’s immune response. Staying hydrated and eating light meals often helps mitigate the discomfort.

7. Fainting

Fainting post-vaccination, though rare, can result from anxiety or a vasovagal response. It’s crucial to sit or lie down immediately if feeling dizzy. Monitoring and resting for a few minutes post-injection can prevent these episodes.

Rare but serious side effects

While most flu shot recipients experience mild side effects, a small fraction might encounter more severe reactions. These can include:

  • Allergic reactions: Symptoms can range from hives to more severe anaphylaxis
  • Guillain-Barré Syndrome (GBS): A rare neurological disorder that the vaccine can trigger in very few cases

If you notice difficulty breathing, facial swelling, or limb weakness after the shot, seek medical attention immediately. Always consult with healthcare professionals if you’re concerned about any post-vaccination symptoms.

Benefits of the flu shot

Beyond its primary function of preventing influenza, the flu shot offers many benefits that extend to both the individual and the community.

  • Protects you against the flu
  • Reduces the severity of illness if you do get it
  • Protects vulnerable populations like people who can’t get a flu vaccination because of other medical issues


Is the flu shot effective immediately after getting it?

No, the flu shot isn’t effective immediately after getting it. The body typically takes about two weeks to develop immunity after receiving the vaccine. During this period, you’re still susceptible to getting the flu. This is why getting the flu shot well before the peak of flu season is always recommended to ensure optimal protection.

Can I get the flu from the flu shot?

No, you can’t get the flu from the flu shot. The injectable flu vaccine contains inactivated (killed) viruses, so they can’t cause an active flu infection. 

However, some people might experience mild side effects after getting the shot, such as soreness at the injection site, mild fever, or muscle aches. These symptoms aren’t the flu but the body’s response to building immunity. 

Why do I need to get a flu shot every year?

You need to get a flu shot yearly primarily because the influenza virus constantly evolves. Due to mutations that occur over time, experts update the flu vaccine yearly to target the most prevalent strains for the upcoming season.

Additionally, the protection the previous year’s flu shot provides gradually decreases, so a fresh vaccination ensures optimal protection. 

Can I get the flu shot if I’m allergic to eggs?

Yes, you can get the flu shot even if you’re allergic to eggs. In addition to egg-based options, flu vaccines come in egg-free alternatives. 

However, you must inform your healthcare provider if you have a severe egg allergy (e.g., anaphylaxis). Your doctor might decide avoiding the vaccine altogether is a better option for you, depending on the severity of your allergy.

Is it safe to get the flu shot during pregnancy?

It’s safe and recommended for pregnant individuals to get the flu shot. The Centers for Disease Control and Prevention (CDC) and other health organizations advocate for flu vaccination during pregnancy. 

This recommendation stems from the heightened risk pregnant individuals face regarding severe complications from the flu due to changes in their immune system, heart, and lungs. 

Also, the flu vaccine offers dual protection. Not only does it shield the mother, but it also confers protection to the baby after birth. When a mother gets vaccinated, she passes on protective antibodies to her fetus, which is important because infants under six months can’t receive the flu vaccine themselves. 

Keep in mind you should consult your doctor before getting the flu shot while you’re pregnant. In some cases, your doctor may not recommend it.

Get coverage for vaccinations

Getting vaccinated remains a pivotal step in safeguarding individual and community health. If concerns arise, always consult with healthcare professionals. Their guidance ensures informed and safe decisions regarding vaccinations. To ensure you have the coverage you need to see the right healthcare providers and get your vaccination, use our online quote tool to find affordable health insurance coverage today.

Related content: