EIU Health Education Resource Center

Flu Facts

If you have any questions or concerns about the flu or the influenza vaccine that are not answered by the information below, please submit your questions HERE and they will be answered in a timely manner.

What is Influenza or the Flu?

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. The best way to prevent flu is by getting a flu vaccine each year. (CDC, 2019)

Flu Symptoms

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 or feeling feverish/chills (fever is not always associated with influenza)
• cough
• sore throat
• runny or stuffy nose
• muscle or body aches
• headaches
• fatigue (tiredness)
• some people may have vomiting and diarrhea, though this is more common in children than adults. These occurrences are rare in adults. (CDC, 2019)

How Flu Spreads

The flu is spread through 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. A person might also 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. (CDC, 2019)

How Many People Get Sick with Flu Every Year?

Approximately 8% of the United States population are infected with influenza every year. (CDC, 2019)

Period of Contagiousness

You may be able to spread 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. (CDC, 2019)

Onset of Symptoms

The time from when a person is exposed and infected with flu to when symptoms begin is about 2 days but can range from about 1 to 4 days. (CDC, 2019)

Complications of Flu

Complications of flu can include bacterial pneumonia, ear infections, sinus infections and worsening of chronic medical conditions, such as congestive heart failure, asthma, or diabetes. (CDC, 2019)

People at High Risk from Flu

Anyone can get flu (even healthy people), and serious problems related to flu can happen at any age, but some people are at high risk of developing serious flu-related complications if they get sick. This includes people 65 years and older, people of any age with certain chronic medical conditions (such as asthma, diabetes, or heart disease), pregnant women, and children younger than 5 years. It is important to note, that while you may not be in one of these high-risk groups, you do have the ability to spread flu to members of these groups. (CDC, 2019)

Preventing Seasonal Flu

The first and most important step in preventing flu is to get a flu vaccine each year. 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. (CDC, 2019)

Treating Flu

There are influenza antiviral drugs that can be used to treat flu illness, but the most effective treatment is prevention, through an annual flu vaccine. (CDC, 2019)

When is Flu Season?

While seasonal influenza viruses are detected year-round in the United States, flu viruses are most common during the fall and winter. The exact timing and duration of flu seasons can vary, but influenza activity often begins to increase in October. Most of the time flu activity peaks between December and February, although activity can last as late as May. (CDC, 2018)

Flu vaccination can keep you from getting sick with flu.

• Flu vaccine prevents millions of illnesses and flu-related doctor’s visits each year. For example, during 2018-2019, flu vaccination prevented an estimated 4.4 million influenza illnesses, 2.3 million influenza-associated medical visits, 58,000 influenza-associated hospitalizations, and 3,500 influenza-associated deaths.
• During seasons when the flu vaccine viruses are similar to circulating flu viruses, flu vaccine has been shown to reduce the risk of having to go to the doctor with flu by 40 percent to 60 percent. (CDC, 2020b)

Flu vaccination can reduce the risk of flu-associated hospitalization for children, working age adults, and older adults.

• Flu vaccine prevents tens of thousands of hospitalizations each year. For example, during 2018-2019 flu vaccination prevented an estimated 58,000 flu-related hospitalizations.
• A 2014 study showed that flu vaccine reduced children’s risk of flu-related pediatric intensive care unit (PICU) admission by 74% during flu seasons from 2010-2012.
• In recent years, flu vaccines have reduced the risk of flu-associated hospitalizations among older adults on average by about 40%.
• A 2018 study showed that from 2012 to 2015, flu vaccination among adults reduced the risk of being admitted to an intensive care unit (ICU) with flu by 82 percent. (CDC, 2020b)

Flu vaccination helps protect women during and after pregnancy.

• Vaccination reduces the risk of flu-associated acute respiratory infection in pregnant women by about one-half.
• A 2018 study that included influenza seasons from 2010-2016 showed that getting a flu shot reduced a pregnant woman’s risk of being hospitalized with flu by an average of 40 percent.
• A number of studies have shown that in addition to helping to protect pregnant women, a flu vaccine given during pregnancy helps protect the baby from flu for several months after birth, when he or she is not old enough to be vaccinated. (CDC, 2020b)

Flu vaccine can be lifesaving in children.

• A 2017 study was the first of its kind to show that flu vaccination can significantly reduce a child’s risk of dying from flu. (CDC, 2020b)

Flu vaccination has been shown in several studies to reduce severity of illness in people who get vaccinated but still get sick.

• A 2017 study showed that flu vaccination reduced deaths, intensive care unit (ICU) admissions, ICU length of stay, and overall duration of hospitalization among hospitalized flu patients.
• A 2018 study showed that among adults hospitalized with flu, vaccinated patients were 59 percent less likely to be admitted to the ICU than those who had not been vaccinated. Among adults in the ICU with flu, vaccinated patients on average spent 4 fewer days in the hospital than those who were not vaccinated. (CDC, 2020b)

Protecting Others

Getting vaccinated yourself may also protect people around you, including those who are more vulnerable to serious flu illness, like babies and young children, older people, and people with certain chronic health conditions. Despite the many benefits offered by flu vaccination, only about half of Americans get an annual flu vaccine and flu continues to cause millions of illnesses, hundreds of thousands of hospitalizations and tens of thousands of deaths. Many more people could be protected from flu if more people got vaccinated. (CDC, 2020b)

Misconceptions about Flu Vaccines

Can a flu vaccine give you flu?

No, flu vaccines cannot cause flu illness. Flu vaccines given with a needle (i.e., flu shots) are made with either inactivated (killed) viruses, or with only a single protein from the flu virus.  The nasal spray vaccine contains live viruses that are attenuated (weakened) so that they will not cause illness. (CDC, 2020a)

Is it better to get sick with flu than to get a flu vaccine?

No. Flu can be a serious disease, particularly among young children, older adults, and people with certain chronic health conditions, such as asthma, heart disease or diabetes. Any flu infection can carry a risk of serious complications, hospitalization, or death, even among otherwise healthy children and adults. Therefore, getting vaccinated is a safer choice than risking illness to obtain immune protection. (CDC, 2020a)

Do I really need a flu vaccine every year?

Yes. CDC recommends a yearly flu vaccine for everyone 6 months of age and older with rare exception. The reason for this is that a person’s immune protection from vaccination declines over time, so an annual vaccination is needed to get the “optimal” or best protection against the flu. Additionally, flu viruses are constantly changing, so the vaccine composition is reviewed each year and updated as needed based on which influenza viruses are making people sick. (CDC, 2020a)

Why do some people not feel well after getting a seasonal flu vaccine?

Some people report having mild side effects after flu vaccination. The most common side effects from flu shots are soreness, redness, tenderness or swelling where the shot was given. Low-grade fever, headache and muscle aches also may occur. If these reactions occur, they usually begin soon after vaccination and last 1-2 days. In randomized, blinded studies, where some people got inactivated flu shots and others got salt-water shots, the only differences in symptoms was increased soreness in the arm and redness at the injection site among people who got a flu shot. There were no differences in terms of body aches, fever, cough, runny nose or sore throat.

Side effects from the nasal spray flu vaccine may include runny nose, wheezing, headache, vomiting, muscle aches, fever, sore throat and cough. If these problems occur, they usually begin soon after vaccination and are mild and short-lived. The most common reactions people have to flu vaccines are considerably less severe than the symptoms caused by actual flu illness. (CDC, 2020a)

Misconceptions about Flu Vaccine Effectiveness

Influenza vaccine effectiveness can vary. The protection provided by a flu vaccine varies from season to season and depends in part on the age and health status of the person getting the vaccine and the similarity or “match” between the viruses in the vaccine and those in circulation. During years when the flu vaccine match is good, the benefits of flu vaccination will vary, depending on factors like the characteristics of the person being vaccinated (for example, their health and age), what influenza viruses are circulating that season and, potentially, which type of flu vaccine was used. (CDC, 2020a)

References

Centers for Disease Control and Prevention. (2018). Influenza (flu): When is flu season. https://www.cdc.gov/flu/about/season/flu-season.htm

Centers for Disease Control and Prevention. (2019). Influenza (flu): What you need to know. https://www.cdc.gov/flu/about/keyfacts.htm

Centers for Disease Control and Prevention. (2020a). Influenza (flu): Misconceptions about flu vaccines. https://www.cdc.gov/flu/prevent/misconceptions.htm

Centers for Disease Control and Prevention. (2020b). Influenza (flu): Vaccine benefits. https://www.cdc.gov/flu/prevent/vaccine-benefits.htm