Feeling sick 3 weeks after flu shot

We might be in for a rough flu season this year in the US, if expert predictions are correct. But the good news is, we have very safe and effective tools for fighting and preventing the flu, caused by the potentially deadly influenza virus, including the flu vaccine.

According to the CDC, flu shots are safe and one of the best ways to keep from getting the flu and spreading it to others. And people who get vaccinated and get sick anyway often experience less severe symptoms. If you're thinking of getting vaccinated for both COVID-19 and the flu, the CDC says it is safe to get both vaccines together (this includes the new COVID-19 boosters).

The simple fact is, flu vaccines can save lives. There are plenty of myths out there about the flu vaccine, such as the idea that it can give you the flu. While that's not true, you can experience some side effects from the flu shot. The side effects are usually mild and nothing to worry about, but it's important to know about them so you're not worried when you get your vaccine.

Below, Dr. Carmen Teague, specialty medical director at Atrium Health's Mecklenburg Medical Group, shares what you need to know about common flu shot side effects that are normal, and which side effects may be a sign of something more serious. 

Read more: 6 Best Vitamins for Flu Season

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 (muscle ache) and even a scant cough," Teague said.

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
• Headache
• Fever
• Nausea
• 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.

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Signs of a more serious (but rare) reaction

"A very small percentage of people can have a true allergic reaction to the vaccine, including chest tightness, difficulty breathing, wheezing, facial or throat swelling and redness of the eyes," Teague said. If you experience these symptoms, you should seek medical attention immediately. Teague says severe allergic reactions usually happen within a few hours of getting the flu shot.

Signs of a severe allergic reaction, according to the CDC, can include:

• Difficulty breathing
• Hoarseness or wheezing
• Swelling around the eyes or lips
• Hives
• Paleness
• Weakness
• A fast heartbeat or dizziness

Another possible reaction is an infection where the shot was administered. "Patients can also develop an infection at the injection site, which is manifested as worsening redness, swelling, warmth and tenderness," Teague said. You should also seek immediate medical attention for this type of reaction. (If you're not sure if it's the common, harmless redness-and-swelling side effect or an infection, check with a doctor.) 

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.

Influenza (flu) is a respiratory virus which is highly contagious. Learn more about the symptoms and the influenza vaccine.

Those who are at risk of serious flu complications such as those 65 and older, young children under the age of 5 and people with certain chronic conditions are strongly recommended to get their yearly flu vaccinations. Flu vaccination, also commonly referred to as a "flu shot", is the best way to prevent the flu.

Influenza, commonly known as the "flu", is a contagious viral disease that can affect anyone, including healthy people. It attacks the respiratory tract in humans (nose, throat, and lungs), causing inflammation of the mucous membranes.

It can be spread when an infected person coughs, sneezes, or speaks. The flu viruses are transmitted into the air through droplets, and other people can be infected when they breathe in the viruses. When these viruses enter the nose, throat, or lungs of a person, they begin to multiply, causing influenza symptoms. The viruses can also be spread indirectly when a person touches a surface with flu viruses on it (for example, a doorknob) and then touches his or her nose or mouth. Transmission can also occur when an infected person shares food with others during mealtime without a serving spoon.

• Flu is usually a more severe condition than the common cold.

• The disease can be deadly to some people who develop life-threatening complications like pneumonia (infection of the lungs).
  

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Causes & Risk Factors

Influenza is caused by the flu virus which has 3 main types: flu A, flu B and flu C. Flu A and B are responsible for seasonal outbreaks and epidemics. Between the two types, flu A causes more severe cases and complications like pneumonia, especially in the elderly, young children (5 years and below) and those with chronic conditions.

Influenza Symptoms and Signs

Flu symptoms usually come on suddenly, and symptoms include high fever, sore throat, coughing, headache, muscle aches, and stuffy nose.

Other symptoms may include sneezing, nasal discharge, loss of appetite, fatigue, weakness, chills, and stomach symptoms.

Complications

A severe case of influenza can lead to pneumonia (infection of the lungs) and other complications such as bronchitis (inflammation of the lungs), sinusitis (infection of the nasal passages), ear infection and meningitis (inflammation of the lining that covers the brain).

Who is more likely to develop complications from an influenza infection?

Persons who get the flu virus may have different reactions to the illness. Some groups of people are at high risk to develop complications which could lead to death. Older people, young children, people with a weakened immune system, or those with heart and lung diseases are more likely to develop serious complications due to a flu infection.

The following people are at highest risk for complications related to influenza infection.

• Persons aged 65 years and older;
• Children who are 6 months to under 5 years old;
• Adults and children who have chronic disorders of the lungs (including asthma) or heart;
• Adults and children who suffer from chronic metabolic diseases (including diabetes); people with kidney malfunction like those on dialysis; those with a blood disorder like thalassemia;
• People whose immune resistance is lowered due to medications or those whose immune system is weakened due to the Human Immunodeficiency Virus (HIV) infection;
• Children and teenagers aged 6 months to 18 years who are receiving long-term aspirin therapy (they are at risk of Reye syndrome, which is a deadly disease that affects all body organs especially the liver and brain, after influenza infection);
• Women who are in the second or third trimester of pregnancy.
  

Related: Know How To Fight Flu

Self-Care

People who develop flu symptoms should practice good self-care. The flu virus takes time and rest to recover. It is important to stay hydrated and avoid strenuous physical activities like running and jogging when ill (until one completely recover). Do not go to work or school and avoid crowded places to minimise the transmission of the infection to others.

Treatment 

Medications to reduce the pain and fever, such as paracetomol, can be used. For higher risk individuals, especially young children, older adults and those with other medical conditions, they should seek medical attention promptly. There are antiviral medications available to treat the flu. These medications act to decrease the ability of flu viruses to reproduce. To be effective, flu antiviral drugs should be taken within the first 2 days after the person gets sick. They may also help reduce the severity of flu symptoms and help the person with flu recover faster by a few days. It is important to remember that these flu antiviral medications are not a substitute for flu vaccination. Getting a flu vaccine yearly is still the best way to protect you from the flu.

Antibiotics are ineffective against the flu because they do not work on viruses. However, sometimes people develop serious secondary infections caused by bacteria in addition to their flu virus.  Secondary bacterial infections may require antibiotic treatment so it is important to have your symptoms assessed by a doctor especially if you are not recovering as expected.

Prevention

There are many ways to prevent the spread of flu and to protect yourself against this infection. Assess the situation you are in. Do you or your household members belong to the group at-risk of developing influenza-related complications? Are you regularly exposed to those at risk of complications from flu? An annual flu vaccine is the best protection for you against the flu.

Additionally, everyone can practise healthy habits, good personal hygiene and be socially responsible.

Wash your hands thoroughly and regularly with soap and water for at least 20 seconds, especially before touching your eyes, nose or mouth and after going to the toilet. While soap and water is the best choice, when it is not available you can follow the same handwashing steps using an alcohol-based hand rub. 

• Cover your mouth and nose with a tissue when coughing or sneezing. If tissue is not available, cough or sneeze into your sleeve so as to prevent the germs from dispersing into the air.
• Wear a surgical mask if you are unwell
• See a doctor if you are feeling unwell
• Do not go to school or work when you are ill
• Never spit in public places
• When sharing food at meal times, use a dedicated serving spoon

Lead a healthy lifestyle

• Eat a balanced diet, including plenty of fruits and vegetables
• Do 30 minutes of physical activity at least 5 days a week
• Have enough sleep and rest. Keep stress levels low
• Do not smoke
  

Related: Protect Yourself And Others Against The Flu

Flu Vaccination - Who Needs It? 

A flu shot is most beneficial for those who have a higher risk of developing complications (see list above) from an influenza infection. Household members of those at risk can also do their part to protect themselves by getting an annual flu shot.

It is also advisable to get a flu vaccination if you are a healthcare worker as you may regularly be exposed to patients with different flu viruses. You will also be protecting vulnerable patients by preventing the spread of the virus to them.

Flu Vaccination - Frequency 

The flu vaccination takes effect about 2 weeks after vaccination, thus it's better to get vaccinated early before flu season starts. In Singapore, the Northern Hemisphere flu season generally occurs between November and February. The Southern Hemisphere season is from May to July. Flu shots contain several strains of flu virus that are expected to be the most common for that season.  

Yearly vaccination is recommended as flu viruses are constantly changing, and your body's immunity to flu viruses may decline over time. Thus, getting vaccinated every year provides the best protection against influenza.

Related: Beat The Flu When You Have Diabetes

Flu Vaccination - Where to Get It and Common Side Effects?

Flu vaccines are offered in many locations, including CHAS GP clinics, polyclinics, hospitals, specialist clinics, nursing homes, workplaces and even schools. 

Some minor side effects can be associated with a flu vaccination. They are:

• Soreness, redness, or swelling where the shot was given
• Muscle aches
• Runny nose
• Headache
• Fever (low grade)
• Cough
• Sore throat
• Vomiting (more likely to happen to children)
  

If these problems occur, they begin soon after the shot and usually lasts 1 to 2 days. These symptoms do not mean you have the flu and unlike the flu, they are not contagious when brought on by the vaccination. On very rare occasions, flu vaccination can cause serious problems, such as severe allergic reactions. Consult your doctor if you have any concerns about your suitability for vaccination.

*Note: This flu vaccine does not give protection against bird flu or the H7N9. Currently, there is no vaccine for this strain.

Subsidies and Use of Medisave for Vaccination

Flu vaccination is highly subsidised at CHAS GP clinics and polyclinics for all Singaporeans who are in the high risk groups.

• Children 6 - 59 months and any child who is in the high-risk groups may get an annual flu shot at no cost

• Singaporean seniors age 65 and above and adults who are in the high-risk groups can get an annual flu shot at subsidised rates at CHAS GP clinics and polyclinics. (Refer to the National Childhood Immunisation Schedule and National Adult Immunisation Schedule.)
  

Additionally, MediSave may be used up to $500/$700 per year for Influenza vaccinations for persons with a higher risk of developing influenza-related complications at both CHAS GP clinics and polyclinics.

 Click here for more information on subsidies available, other vaccine-preventable diseases and frequently asked questions.

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Read these next:

• FIGHT The Spread Of Infectious Diseases
• Interesting Beliefs About Sneezing
• 4 Reasons to Get Vaccinated—Adult Immunisation

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