What to Avoid After Flu Shot: Precautions and Aftercare Steps

A woman with flu shot
  • Flu shots offer protection against flu viruses, and more Americans are getting vaccinated each year.

  • Following proper steps before a flu shot can make the vaccination process easier and decrease your chances of a severe allergic reaction.

  • It’s recommended to eat well and stay hydrated to avoid fainting spells after your flu shot.

  • There are typically no restrictions you should follow post-vaccination, but resting well is advised.

Imagine bypassing the misery of flu season — the fever, aches, and persistent fatigue. With 51.6% of Americans now vaccinated yearly, a flu shot is your way out.

But how do you prepare for a flu shot, and what do you do afterward to minimize potential side effects?

What is a Flu Shot?

The term "flu shot" commonly refers to the vaccine administered to protect against influenza viruses. It targets both Influenza A and B (these viruses commonly affect humans).

Like other vaccinations, the flu shot is designed to:

  • Provide immunity to a disease

  • Decrease the length and severity of an illness

  • Minimize hospitalizations

  • Limit the spread of infection

There are a range of influenza vaccines available. These vary in their coverage against different virus strains, their method of administration, and their specific vaccine composition.

These days, the term “shot” might be misleading, because not all influenza immunizations are injected — a nasal spray flu vaccine is also available.

How Does a Flu Shot Protect Against Influenza?

The human body defends itself against external invaders through its immune system, which comprises two main parts: the innate and acquired immune systems.

The innate immune system, present from birth, provides general, nonspecific defense against various pathogens using mechanisms like the skin as a barrier.

The acquired or adaptive immune system develops from exposure to pathogens, such as influenza, and creates antibodies to target specific germs.

This system includes memory cells that retain defense strategies against previously encountered illnesses, enabling a faster and more efficient response to subsequent infections.

Flu vaccines work by simulating attacks to prompt the acquired immune system to develop defenses against specific pathogens, thus building immunity without experiencing the actual illness.

Why do I need an annual flu vaccination?

Influenza A and B often mutate. With each flu season, these viruses may have changed enough to render previous immunity ineffective, so it’s best to play it safe and get a flu shot each year.

Key Point: Who Should Get Flu Shots?

Flu shots are recommended for most people, but those at high risk of getting severely ill are strongly encouraged to get vaccinated. These people include:

  • Pregnant women: Research shows that pregnant women who receive the flu vaccine may halve their risk of getting sick and decrease their chances of passing the virus to their unborn children.
  • Anyone over 65
  • Individuals with weak immunity, such as people undergoing chemotherapy or those living with HIV
  • People with other illnesses like diabetes, cardiovascular diseases, asthma, chronic obstructive pulmonary disease, or kidney and/or liver problems. These are known as comorbid diseases.
  • People without a normal-functioning spleen
  • Children older than 6 months

What Should I Know Before I Receive a Flu Shot?

Before we get to the aftercare steps for flu shots, there are a few things you need to know and do before you get vaccinated.

Being properly prepared before your flu shot will minimize side effects and help you avoid a severe allergic reaction.

Find out what your allergies are

It’s crucial to be aware of any allergies you may have when considering vaccinations. There has been some controversy around egg-based vaccines.

However, as of 2023, the Centers for Disease Control and Prevention (CDC) no longer recommends withholding egg-based vaccines from those with egg allergies.

Despite this, we still advise you to get vaccinated in a clinical setting where allergic reactions can be promptly treated.

Verify which vaccine you’ll be taking

Immune-compromised individuals, those without a normal-functioning spleen, pregnant women, and people with other serious medical conditions should not use live attenuated influenza vaccinations. These have the word “LAIV” in their names — your doctor will be able to advise you.

Note the time of year

The CDC recommends giving vaccines to most people in the Northern Hemisphere in September or October.

Administering it any earlier may result in your immunity wearing off before the flu season even starts (typically between December and March).

While there are guidelines regarding the timing of vaccinations, the vaccine may still be given at other times if there are ongoing flu cases in your area.

There are other exceptions to treatment guidelines, but these need to be discussed with your healthcare provider, especially if you are pregnant or have existing health conditions.

Other precautions

Here are some other important things you should know before getting vaccinated against influenza:

  • Children less than 6 months old shouldn’t receive flu vaccines.

  • Formaldehyde is present in certain vaccines to neutralize toxins from vaccines. This chemical is typically diluted during the vaccine manufacturing process. At higher levels, formaldehyde is harmful to humans, but the level found in vaccines is generally safe.

  • If you intend to vaccinate yourself against influenza for travel purposes, the vaccine needs to be taken at least two weeks prior to travel for it to be effective.

  • Taking antiviral medications such as oseltamivir (Tamiflu®), baloxavir marboxil (Xofluza®) and peramivir (RapiVab®) may reduce the effectiveness of your flu shot, so it’s recommended to avoid these.

If you’ve recently had the flu and you’ve taken any antiviral medication, always consult your healthcare provider to determine whether you are eligible for the flu vaccination — taking antivirals before or shortly after your vaccination can decrease the immunity gained from it.

Key Point: What are the Different Types of Flu Shots?

There are several types of flu vaccines, each designed to stimulate the immune system in a different way.

  • Inactivated influenza virus (IIV): Contains a “dead” form of the influenza virus, stimulating the immune system without causing the disease
  • Recombinant influenza vaccine (RIV): Rather than using the actual virus, virus genes are inserted into another organism to produce influenza-like antigens
  • Live attenuated influenza vaccine (LAIV): Contains a “live”, but weakened, influenza virus, generating a strong immune response, though it may cause mild illness in some cases

Your healthcare provider will determine which one of these is right for you.

What Should I Watch Out for After a Flu Shot?

Care needs to be taken when using flu shots alongside other vaccinations. Always consult your healthcare provider to determine how long you should wait between vaccinations.

Flu shot side effects

If you decide to get a flu shot, you should be aware of potential side effects, which can vary from mild to more serious. Some common side effects of flu shots include:

  • Irritation or discomfort at the site of injection

  • Muscle aches

  • Fever

  • Drowsiness or fatigue

More severe symptoms that may indicate anaphylaxis include:

  • Breathing difficulties

  • Facial swelling, particularly around the lips, tongue, and eyes

  • Wheezing

  • Dizziness

  • Pale skin

  • Diarrhea and vomiting

  • Fainting

  • Rashes: Look out for hives, which are itchy red bumps that can appear soon after vaccination. This may indicate an allergy to a component of the flu vaccine. If hives appear, consult your healthcare provider immediately — even if it doesn't seem serious.

Key Point: What to Do if You Have a Serious Reaction to a Flu Shot

Anaphylaxis is a medical emergency. Vaccinations should be done in a facility capable of managing anaphylaxis, should it occur. The treatment of choice for this condition is epinephrine (adrenaline) injected into the muscle.

Here are some steps you can follow if you have a severe reaction to a flu vaccine:

  1. If you have a known allergy and carry epinephrine, use it on the outer mid-thigh. The dose for adults is 0.5 mg in the thigh muscle. Ideally, use an epinephrine auto-injector, such as an EpiPen®. You can repeat this in 5 minutes if there’s no improvement in your symptoms.

  2. Call for help immediately, especially if you have no epinephrine. Dial 911 and explain the situation. If possible, have someone you trust keep an eye on your condition in case your symptoms worsen.

  3. Do not attempt to get up and drive. Lie flat with your legs elevated. Always ask the paramedic dispatcher for advice regarding waiting for the ambulance or having someone drive you. Remember, even though you may get to the hospital faster on your own, paramedics can administer life-saving adrenaline as soon as they reach you.

  4. Consult your healthcare practitioner even if you’re feeling better.

  5. Once discharged from your healthcare facility, get a medical bracelet stating the cause of your severe allergic reaction. You may also need to carry epinephrine with you.

A note on epinephrine auto-injectors:

EpiPens® are considered a first-line treatment for anaphylaxis. If you’re in an emergency situation, you may not have time to draw up medication from a vial and measure it accurately, so an auto-injector pen is the preferred option.

What Should I Avoid After a Flu Shot?

There are no restrictions you should follow after getting a flu shot, but some soreness at the injection site is common.

Therefore, you may want to rest up after your vaccination and not schedule any strenuous activities directly after.

Flu Vaccine Safety: How to Reduce Arm Soreness and Stay Comfortable After a Flu Shot

To ensure comfort and reduce arm soreness after receiving a flu vaccine, follow these steps:

  • Stay relaxed: During the injection, try to remain calm and relax your body. Tensing up can increase the pain.

  • Positioning: Sit or lie down during your vaccination to reduce the risk of injury from fainting.

  • Topical anesthetics: Your healthcare provider might offer a topical anesthetic like Lidocaine-Prilocaine (EMLA®) to numb the area before vaccination. This can also be bought over the counter at a pharmacy.

  • Ice application: Applying ice to the area beforehand can lessen injection pain.

  • Avoid pulling away: Do not jerk away from the injection, as this could cause injury and increase pain.

  • Manage pain: After the injection, painkillers such as acetaminophen can help alleviate discomfort. Children should avoid aspirin post-vaccination.

Are There Certain Foods I Should Avoid After a Flu Shot?

There are no specific dietary restrictions before or after receiving an influenza vaccine, but staying hydrated and eating a balanced meal beforehand can be beneficial.

Eating before a flu shot is particularly important for individuals prone to fainting due to vasovagal syncope, a condition where overstimulation of the vagus nerve leads to a sudden drop in blood pressure and fainting.

Adequate hydration helps maintain blood volume, reducing the likelihood of fainting, while eating can prevent hypoglycemia (another factor that may increase the risk of fainting).

Where Can I Learn More About Flu Vaccines?

Want to beat those winter sniffles this year? LifeMD can help.

LifeMD can connect you to a team of healthcare professionals who can answer all your questions and concerns about flu vaccines and schedule your flu shot for when it suits you best.

Book your appointment today to get started.

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This article is intended for informational purposes only and should not be considered medical advice. Consult a healthcare professional or call a doctor in the case of a medical emergency.

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