COVID Testing & Safety

On this page find information about the flu virus, vaccines, and flu vaccine safety.

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Flu Virus

  • Flu is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and sometimes the lungs. It can cause mild to severe illness, and at times can lead to death.

  • Influenza (flu) can cause mild to severe illness, and at times can lead to death. Flu is different from a cold. Flu usually comes on suddenly. People who have flu often feel some or all of these symptoms: fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, tiredness, and some people may have vomiting and diarrhea, though this is more common in children than adults.

  • Most experts believe that flu viruses are spread mainly by tiny droplets made when people with flu cough, sneeze, or talk. These droplets can land in the mouths or noses of people who are nearby. Less often, a person might get flu by touching a surface or object that has flu virus on it and then touching their own mouth, nose, or possibly their eyes.

  • You may be able to spread the flu to someone else before you know you are sick, as well as while you are sick.

    People with flu are most contagious in the first 3-4 days after their illness begins.

    Some otherwise healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5 to 7 days after becoming sick.

    Some people, especially young children and people with weakened immune systems, might be able to infect others for an even longer time.

  • The first and most important step in preventing flu is to get a flu vaccine each year. The flu vaccine has been shown to reduce flu-related illnesses and the risk of serious flu complications that can result in hospitalization or even death. CDC also recommends everyday preventive actions (like staying away from people who are sick, covering coughs and sneezes, and frequent handwashing) to help slow the spread of germs that cause respiratory (nose, throat, and lungs) illnesses, like flu.

  • It is very difficult to distinguish flu from other viral or bacterial respiratory illnesses based on symptoms alone. There are tests available to diagnose flu. If you begin to feel symptoms, the first best step is to get in touch with your doctor to schedule an appointment.

Flu Vaccine

  • Because the flu is a respiratory infection that can cause serious complications, getting a flu (influenza) vaccine is the best way to prevent the misery of the flu and its complications. The Centers for Disease Control and Prevention (CDC) recommends annual flu vaccination for everyone age 6 months or older. A flu vaccine helps your immune system build specific antibodies that fight the flu and help your body fight the virus if you come into contact with it.

  • It’s best to be vaccinated before flu begins spreading in your community. September and October are generally good times to be vaccinated against flu. Ideally, everyone should be vaccinated by the end of October. However, even if you are not able to get vaccinated until November or later, vaccination is still recommended because flu most commonly peaks in February and significant activity can continue into May.

  • Because flu viruses evolve so quickly, last year's vaccine may not protect you from this year's viruses. New flu vaccines are released every year to keep up with rapidly adapting flu viruses. When you get vaccinated, your immune system produces antibodies to protect you from the viruses included in the vaccine. But antibody levels may decline over time — another reason to get a flu shot every year.

  • The CDC recommends annual flu vaccinations for everyone age six months or older. Vaccination is especially important for people at high risk of influenza complications, including:

    -Pregnant women
    -Older adults
    -Young children
    -People with weakened immune systems

    Children between six months and eight years may need two doses of the flu vaccine, given at least four weeks apart, the first time they are given a flu vaccine. After that, they can receive single annual doses of the flu vaccine. A 2017 study showed that the vaccine significantly reduces a child's risk of dying of the flu. Check with your child's doctor.

  • No, the flu vaccine will be available as an injection or as a nasal spray. The nasal spray vaccine is approved for people between two and 49 years old. However, it is important to note that there are other groups advised to be cautious about the use of a nasal spray flu vaccine, such as people with certain chronic medical conditions. It is best to consult with a health provider to see if you need to be cautious about getting a nasal spray flu vaccine.

  • No. The flu vaccine can't give you the flu. It also does not increase your risk of COVID-19. But you might develop flu-like symptoms — despite getting a flu vaccine — for a variety of reasons, including:

    Reaction to the vaccine. Some people experience muscle aches and a fever for a day or two after receiving a flu vaccine. This may be a side effect of your body's production of protective antibodies.

    The two-week window. It takes about two weeks for the flu vaccine to take full effect. If you're exposed to the influenza virus shortly before or during that time period, you might catch flu.

    Mismatched flu viruses. In some years, the influenza viruses used for the vaccine don't match the viruses circulating during the flu season. If this occurs, your flu vaccine will be less effective, but will still offer some protection.

    Other illnesses. Many other illnesses, such as the common cold, also produce flu-like symptoms. So, you may think you have flu when you actually don't.

Flu Vaccine Safety

  • Flu vaccines have a good safety record. Hundreds of millions of Americans have safely received flu vaccines over the past 50 years, and there has been extensive research supporting the safety of flu vaccines. A flu vaccine is the first and best way to reduce your chances of getting flu and spreading it to others. CDC recommends that everyone six months of age and older receive a flu vaccine every year.

  • 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 vaccine include:
    -Soreness, redness, and/or swelling from the shot
    -Headache
    -Fever
    -Nausea
    -Muscle aches

  • With any vaccine, look for any unusual conditions, such as a high fever, behavior changes, or signs of a severe allergic reaction after vaccination.

    Signs of a severe allergic reaction can include:
    -Difficulty breathing
    -Hoarseness or wheezing
    -Swelling around the eyes or lips
    -Hives
    -Paleness
    -Weakness
    -A fast heartbeat or dizziness

    Life-threatening allergic reactions to the flu vaccine are rare. These signs would most likely happen within a few minutes to a few hours after the vaccine is given.

  • If you think it is a severe allergic reaction or other emergencies that can’t wait, call 9-1-1 and get to the nearest hospital. Otherwise, call your doctor.

  • CDC recommends everyone six months of age and older should receive an annual flu vaccination with rare exceptions. Individuals who can’t get the flu shot include: -Children younger than six months, since they are too young to get a flu vaccine.
    -Individuals with severe, life-threatening allergies to flu vaccine or any ingredient(s) in the vaccine.

    Individuals should talk with their doctor before getting the flu vaccine if they:
    -    Have had a severe allergy to eggs or any of the ingredients in the vaccine.
    -Have had Guillain-Barré syndrome (GBS).
    -Are not feeling well.

  • CDC and the Food and Drug Administration (FDA) 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 (VAERS): 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 (VSD): A collaboration between CDC and nine health care organizations that allows ongoing monitoring and proactive searches of vaccine-related data.

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Information on this page are sourced from the Centers for Disease Control, Medical College of Wisconsin, and Johns Hopkins Medicine.