Feeling Sick After Flu Shot

Can You Get The Flu From The Flu Shot

A doctor explains why you feel terrible after a flu shot

As the warm summer days begin to fade and the air starts to turn crisp,myths surrounding the flu vaccine begin to circulateseemingly as contagious as the flu virus itself. The most common things we hear are related to concerns of getting the flu from the flu shot and patients telling us that they are very healthy and never get the flu, saysInessa Gendlina, MD, Ph.D., an assistant professor of infectious diseases at Montefiore Health System.

Other myths include not needing to be vaccinated every year to maintain immunization, the flu vaccine not being very effective, and the flu not being very dangerous. With all these misconceptions swirling about,fewer than half of adults in the United States get vaccinated annually, even though an estimated 359,000 Americansdied from the flu between 2010 and 2020.

Although its common to experience some mild side effects from the flu vaccine, serious reactions are very rare, and getting the flu from the vaccine isnt possible. Heres how to know what to expect.

Can You Get Sick After Getting A Vaccine

Key takeaways:

Vaccines like the flu shot cant make you sick, but they can cause side effects.
Side effects are generally mild and are different from serious allergic reactions.
If you have questions about a vaccine or are unsure if it is safe for you, talk to your healthcare provider.

Feeling sick after getting a vaccine like the flu shot can be frustrating, especially if it gets in the way of your daily activities. You may wonder if the vaccine made you sick or if you had a reaction to it. You might also wonder if its safe to get the vaccine again in the future, if you need it. Keep reading to find out more about what it means if you dont feel well after a vaccine.

How Is The Safety Of Flu Vaccines Monitored

CDC and the Food and Drug Administration closely monitor the safety of vaccines approved for use in the United States. CDC uses two primary systems to monitor the safety of flu vaccines:

Vaccine Adverse Event Reporting System : an early warning system that helps CDC and FDA monitor problems following vaccination. Anyone can report possible vaccine side effects to VAERS. Generally, VAERS reports cannot determine if an adverse event was caused by a vaccine, but these reports can help determine if further investigations are needed.

Vaccine Safety Datalink : A collaboration between CDC and nine health care organizations which allows ongoing monitoring and proactive searches of vaccine-related data.

People with egg allergies can receive any licensed, recommended age-appropriate influenza vaccine that is otherwise appropriate. People who have a history of severe egg allergy should be vaccinated in a medical setting, supervised by a health care provider who is able to recognize and manage severe allergic reactions. Two completely egg-free flu vaccine options are available: quadrivalent recombinant vaccine and quadrivalent cell-based vaccine.

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Do Flu Vaccines Cause Any Side Effects

Like any medical product, vaccines can cause side effects. Side effects of the flu vaccine are generally mild and go away on their own within a few days.

Common side effects from the flu shot include:

Soreness, redness, and/or swelling from the shot
Muscle aches

The flu shot, like other injections, can occasionally cause fainting.

Some studies have found a possible small association of injectable flu vaccine with Guillain-Barré syndrome . Overall, these studies estimated the risk for GBS after vaccination as fewer than 1 or 2 cases of GBS per one million people vaccinated. Other studies have not found any association. GBS also, rarely, occurs after flu illness. Even though GBS following flu illness is rare, GBS is more common following flu illness than following flu vaccination. GBS has not been associated with the nasal spray vaccine.

Can The Flu Vaccine Make You Sick

Is it normal to feel sick after the flu shot?

Lets just clear this up now: You cant get the flu from the flu vaccine, Dr. Adalja says. Seriously, this is not a thing that is even remotely possible.

However, in very rare cases, a flu vaccine can cause issues in people with pre-existing medical circumstances. The flu vaccine is safe for most people, but if you have any allergies, like to egg proteins or any other ingredients that could be in the vaccine, such as gelatin, its important to speak with your doctor or pharmacist before getting inoculated. Those with an egg allergy can get the flu vaccine, but need to discuss with their doctor which specific vaccine is right for them, Dr. Agarwal says.

Overall, the CDC recommends speaking to a health care professional prior to getting a flu vaccine if you meet any of the following criteria:

Youre allergic to eggs or any other potential vaccine ingredients, such as gelatin.
Youve ever had Guillain-Barré Syndrome .
Youre not feeling well.

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Myth #: Waiting Until Winter For A Flu Shot Is Safer

Fact: While peak flu season is between December and February, you can get sick as early as October. Some believe that getting vaccinated later will protect them longer, which is simply false. This also leaves you exposed for weeks, or months while the virus is floating around.

Also, an annual flu shot helps your body build immunity for the types of influenza viruses that research indicates will be the most common that season. But immunity isnt built as soon as you get the shot. How long does it take for the flu shot to take effect? Two weeks which is another reason to schedule your flu shot early.

While getting your flu shot as soon as the vaccine is available offers the best protection, the CDC recommends everyone 6 months and older get vaccinated by the end of October. Pregnant people particularly those in their third trimester of pregnancy should receive a flu shot as soon as the vaccine becomes available.

How The Influenza Vaccine Works

The influenza viruses change every year because the influenza virus has a unique ability to change its surface structure. This means that even if you had the flu or an immunisation one year, your bodys immune system might be unable to fight the changed version of the virus that will be circulating the following year.

Each year, a new vaccine is developed and is available for those who wish to be immunised. The seasonal flu vaccine includes protection against four strains of influenza viruses.

The flu vaccine cannot give you the flu because it does not contain live virus. Some people may still contract the flu because the vaccine may not always protect against all strains of the influenza virus circulating in the community.

Feeling Sick After Getting A Flu Shot Is A Normal Thing

The intent of flu shots is to avoid the flu. We know this. Its been drilled into our heads again and again. And yet, a little less than half of adults in the US got the routine jab for the 2018 to 2019 flu season.

The reason for this shouldnt be the costmost insurance and Medicaid covers the flu vaccine as preventative medicine. Nor should it be conveniencethe US passed a law in August allowing pharmacists across all 50 states to give flu shots. Instead, its the myth that the flu shot itself makes you sick.

Like most misconceptions that stick around, theres a little truth to it. Its normal to feel peakyfatigued, achey, or warm with a low-grade feverafter getting a flu shot. This is the robust immune response as the bodys creating antibodies, actual protection against the flu, says Juanita Mora, an immunologist practicing in Chicago and volunteer medical spokesperson with the American Lung Association. It happens to about 10% of people who get the shot, she says.

In other words, feeling like youre in the early stages of getting the flu is actually a sign that youll be protected from the actual virus. What youre feeling is the bodys defense system gearing up.

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Reaction At The Injection Site

Why Do You Feel Bad After a Flu Shot?

The most common side effect of the flu shot is a reaction at the injection site, which is typically on the upper arm. After the shot is given, you may have soreness, redness, warmth, and in some cases, slight swelling. These effects usually last less than two days.

To help reduce discomfort, try taking some ibuprofen before getting your shot.

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Who Should And Who Should Not Get A Flu Vaccine

Everyone 6 months of age and older should get an influenza vaccine every season with rare exception. CDCs Advisory Committee on Immunization Practices has made this recommendation since the 2010-2011 flu season.

Vaccination to prevent flu and its potentially serious complications is particularly important for people who are at higher risk of developing serious flu complications. See People at Higher Risk of Developing Flu-Related Complications for a full list of age and health factors that confer increased risk.

Special Consideration Regarding Egg Allergy

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Common Flu Shot Side Effects

Repeat: The flu vaccine won’t give you the flu, but you can experience mild symptoms because of how the vaccine works.

“The flu vaccine is designed to stimulate your immune system to build antibodies to the virus. That stimulation can cause a low-grade fever, a decrease in appetite, loose stool, mild fatigue or myalgia and even a scant cough,” Teague says.

According to Teague, these symptoms usually resolve after a few days and are no cause for alarm. You may also experience some redness, swelling or soreness where the shot was injected, which is also normal.

The CDC says you can experience “flulike” symptoms after getting the vaccine, such as:

Soreness, redness, and/or swelling at the injection site
Muscle aches

The symptoms listed above should resolve in a few days. Also, keep in mind not everyone has symptoms, but those are the most common. When it comes to other symptoms, or symptoms that last longer, it’s important to keep in mind that you can still catch a cold, or other virus, right after you get the flu shot.

So if you experience other symptoms that seem like the flu, it could be another illness and it doesn’t mean the shot made you sick. The flu shot also takes about two weeks to become effective at protecting you from the flu, so you could technically catch the flu within that two-week window.

Are Vaccine Side Effects A Good Sign

Feeling sick after getting a flu shot is a normal (and even good!) thing

If you have side effects to a vaccine, that means your immune system is responding. In other words, mild side effects are normal and mean that your body is doing the right thing.

It is also possible not to have any side effects after your shot. This doesnt mean that the vaccine isnt working, however. In fact, not everyone develops side effects after the COVID-19 vaccine. For example, about 33% of people in clinical trials for the Pfizer-BioNTech vaccine did not report any side effects beyond redness, pain, or swelling where the shot was given. But the clinical trials showed the vaccines are still highly efficacious, even though not everyone in the studies had side effects.

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Are Any Of The Available Flu Vaccines Recommended Over Others

Yes, for some people. For the 2022-2023 flu season, there are three flu vaccines that are preferentially recommended for people 65 years and older. These are Fluzone High-DoseQuadrivalent vaccine, Flublok Quadrivalent recombinantflu vaccine or Fluad Quadrivalent adjuvanted flu vaccine. On June 22, 2022, CDCs Advisory Committee on Immunization Practices voted unanimously to preferentially recommend these vaccines overstandard-dose unadjuvanted flu vaccines. This recommendation was based on a review of available studies which suggests that, in this age group, these vaccines are potentially more effective than standard dose unadjuvanted flu vaccines. There is no preferential recommendation for people younger than 65 years.

Can A Flu Shot Make You Get Sick

It isnt out of the ordinary to react to the flu shot, as its simply a sign that your immune system getting to work protecting you. Common responses include a sore arm, headache, nausea, muscle aches or a mild fever. The vaccine itself is adapted every year, Dr. Ford says. So its very hard to predict, from one year to the next, if youre going to have a mild reaction, no reaction or a more problematic reaction.

However, if you do get sick after getting a flu shot, its not because of the vaccine. The only direct reactions to the shot are going to happen within the first 24 to 48 hours, Dr. Ford affirms. As mentioned before, if you get sick after that, people might think its related to getting the flu shot. But its just a coincidence.

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Okay But What Temperature Is Considered Normal

Both adults and children will likely develop a low-grade fever getting vaccinated, and your temperature should return to baseline after just one or two days, Dr. Whyte explains. While definitions vary slightly, a low-grade fever is typically less than 100.5 degrees.

It’s common to get a low-grade fever after a flu shot, which is typically less than 100.5 degrees.

If a fever persists over the course of a few days and rises above 101 degrees, especially if youve already taken a fever reducer, you might be experiencing a high-grade fever. In this case, Dr. Whyte says you should probably head to your doctor’s office for a checkup.

What Are The Benefits Of Flu Vaccination

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There are many reasons to get an influenza vaccine each year. Below is a summary of the benefits of flu vaccination and selected scientific studies that support these benefits.

Flu vaccination can keep you from getting sick with the flu.

Flu vaccination can reduce the risk of flu-associated hospitalization for children, working-age adults, and older adults.
Flu vaccination is an important preventive tool for people with chronic health conditions.

Flu vaccination has been associated with lower rates of some cardiac events among people with heart disease, especially among those who had had a cardiac event in the past year.
Flu vaccination can reduce worsening and hospitalization for flu-related chronic lung disease, such as in persons with chronic obstructive pulmonary disease.
Flu vaccination also has been shown in separate studies to be associated with reduced hospitalizations among people with diabetes and chronic lung disease.

Flu vaccination helps protect women during and after pregnancy.
Flu vaccines can be lifesaving in children.
Flu vaccination has been shown in several studies to reduce the severity of illness in people who get vaccinated but still get sick.

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Common Side Effects Of The Flu Vaccine

Some people don’t experience any side effects after a flu jab. But the most common reactions are:

a sore arm, or pain, itching, or redness at the injection site
aches and pains
feeling feverish, tired, or unwell

These are normal responses to the vaccine.

You may be asked to wait 15 to 20 minutes after your vaccination so that treatment can be given quickly if a very rare, severe allergic reaction occurs. Many people aged 13 years and older will only need to wait 5minutes. Children under 13 years will need to wait 20 minutes.

Allergic responses are extremely rare.

Why Is The Flu Vaccine Recommended

While the flu vaccine isn’t 100% effective, it still greatly lowers a person’s chances of catching the flu, which can be very serious. It also can make symptoms less severe if someone who got the vaccine does still get the flu.

If you got the flu vaccine last year, it can’t provide enough protection this year, because flu viruses change. That’s why the vaccine is updated each year to include the most current types of the virus.

Sometimes the same virus types are included in the vaccine from one year to the next. Even then, it’s still important to get the yearly flu vaccine because the body’s immunity against the influenza virus declines over time.

Getting the flu vaccine not only protects you from the flu. It also helps protect the people and community around you. The flu vaccine makes someone less likely to get the flu, and therefore less likely to spread the flu. Getting the flu vaccine is a great way to protect people who are at risk from flu, such as the elderly, babies, and people with health conditions such as asthma. Every year thousands of people die from influenza, and getting the flu vaccine is one way to help prevent that.

What Is A Flu Vaccine

Influenza vaccines are vaccines that protect against the four influenza viruses that research indicates will be most common during the upcoming season. Most flu vaccines are flu shots given with a needle, usually in the arm, but there also is a nasal spray flu vaccine.