Influenza: Deadly Myths and Sickening Facts

This winter the influenza virus is hitting the country especially hard. A major reason for this tougher-than-usual flu season is that this year’s most prevalent strain of the influenza virus is especially nasty.

There are four different species of influenza virus known as A, B, C, and D, with the seasonal flu being caused by influenza A and B viruses. In over 80% of cases of flu this year, the culprit has been a strain of the influenza A virus known as H3N2. H3N2 causes more health consequences, is harder to prevent, and can be especially deadly for vulnerable populations like children, the elderly, and those with compromised immune systems. The reason H3N2 is harder to prevent is because it mutates more than other strains which means that even though this year’s flu vaccine did include the H3N2 strain, it might not be as effective in preventing people from getting the flu this year.

So, knowing that, should you still get the flu shot? The answer is a resounding yes. Remember that the flu shot is not about completely eliminating your risk of getting the flu, but rather reducing it. This means that even a vaccine that is less effective still has benefit in reducing your chance of illness and possible death.

There are many myths that surround the influenza vaccine and they can often lead to confusion and to fewer people receiving the vaccine. As health care professionals, people might come to you with questions and concerns about the flu shot and trust that you will able to provide them with answers and information. In this article, we will review some of the basics of how the flu virus is spread as well as the symptoms it can cause before focusing our attention on dispelling eleven major myths that surround the flu and the flu shot.

How It Spreads

The influenza virus spreads from person to person by several different routes. It can be transmitted through large-particle respiratory droplets if people are near each other, or through the air by small-particle residues of evaporated droplets. A third way it can be transmitted is when someone comes in contact with a respiratory-droplet contaminated surface.

The typical incubation period for the virus is one to four days, with most people beginning to show symptoms by day two. Once infected, an adult is considered contagious from the day before they start to show symptoms and for between five and 10 days after that. For children, they may be contagious for several days before they show symptoms and for 10 or more days beyond that. A person who is severely immunocompromised can shed virus particles for weeks or month after they are infected. Roughly 20% to 30% of people carrying the influenza virus have no symptoms.

Symptoms of Influenza

The usual first symptoms of influenza include chills and a fever with temperatures usually ranging from 100°F to 103°F. Other symptoms of influenza include cough, nasal congestion, sore throat, headache, fatigue, muscle and joint pain, and vomiting. Early on in its disease course, it can be difficult to distinguish between influenza and the common cold virus. Since the treatment of influenza with an antiviral drug are most effective if given sooner, it can be important to identify influenza early. Of the symptoms listed, the ones that have been found most important for diagnostic accuracy are a combination of fever, cough, and sore throat and/or nasal congestion.

Myth #1: It is now too late for me to get the flu shot!

The flu season typically peaks sometime between December and January, but after it peaks, it still takes many weeks for the virus to slow down. In some years, the flu season can continue on into May. While it takes roughly two weeks to develop immunity after receiving the flu shot, the minimal risk associated with the vaccination and its potential benefits of avoiding serious illness and possibly death still makes getting the flu shot a good idea.

Myth #2: The flu shot actually has the potential to give you influenza.

The flu shot is currently made either with an inactivated virus that lacks the ability to infect, known as the inactivated flu vaccine, or with no flu virus at all, known as the recombinant flu vaccine. The most common side effect of receiving the flu shot is soreness, redness, swelling, or tenderness at the site of the injection. Less common reactions include a mild fever and muscle aches which, on the rare instances they do occur, begin soon after receiving the flu shot and resolve in one to two days.

Multiple studies examining the side effects of the flu shot have been done where people were divided into two groups. One group received a flu shot and other group received a salt-water shot. Neither the person getting the shot or the person giving the shot knew which group they were in. The studies found that the only difference in symptoms between the two groups were increased redness and soreness at the site of injection in those that received the flu shot. There were no differences in terms of body aches, fever, cough, runny nose, or sore throat.

Myth #3: It is better to get the flu than to get a flu shot.

As we mentioned previously, influenza can be deadly. Groups that are at a particularly high risk are young children, older adults, and those with certain chronic health conditions like asthma, heart disease, and diabetes. The flu is more than just an unfortunate illness, it can be extremely deadly. In the United States alone, roughly 36,000 people die and another 200,000 people are hospitalized each year because of the flu. In fact, influenza, in combination with pneumonia, is currently the eighth leading cause of death in the United States. No one likes shots, but getting the flu can be much worse.

Myth #4: Some types of flu shots are better than others.

Among the many recommended and approved injectable influenza vaccines, there is no one vaccine that is preferred over others. The most important thing is for everyone 6 months and older to get the flu shot every year.

Myth #5: The flu shot does not work because I got the shot and still got sick with the flu symptoms.

There are four general reasons why this might happen. The first possible reason is that the person got sick from another respiratory virus like rhinoviruses, which can cause symptoms similar to the flu and is very common during the flu season. The influenza vaccine will only protect you from the influenza virus.

The second reason is that the person was exposed to the flu virus before receiving the vaccination or in the two-week period after receiving the vaccination. From the time you receive the flu shot, it typically takes about two weeks for the body to develop the antibodies needed to protect your body from the flu virus.

A third reason that someone might get sick with flu symptoms even though they got the flu shot is that they may have been exposed to a type of flu virus that is very different from the particular virus that the vaccine is designed to protect against. Each year the vaccine is produced based on what the CDC projects as the most likely strains of influenza to be present. The vaccine is usually trivalent, or composed of three separate components, with each component selected to protect against one of three main influenza viruses. The influenza vaccine is approximately 40% to 60% effective in preventing someone from contracting influenza, although this number will vary from year to year depending on the influenza strain that is being covered.

The fourth and final reason for someone experiencing flu symptoms after vaccination is that the flu vaccine can vary in how well it protects people from getting sick with the flu. Remember that the flu shot does not completely eliminate your chance of getting the flu but it does reduce your risk.

Myth #6: Getting the flu shot one year can protect you from the flu for multiple years.

Each year the flu vaccine is designed to specifically protect people from that season’s influenza virus. Even when the virus that the vaccine protects you from has not changed from the previous year, the recommendation is still to get a flu shot every year. This is due to the fact that the immune protection offered by the flu vaccine declines over time and an annual flu shot is needed to give you the best protection from getting the flu.

Myth #7: You should wait to get vaccinated as long as possible so that your immunity lasts to the end of flu season.

It takes about two weeks after getting vaccinated for the antibodies that will fight the flu virus to develop. Because of this delay, it is recommended that people get vaccinated starting in the end of October before the virus really begins to spread. Although the length of immunity gained from the vaccine can vary between people, studies suggest that, for most people, their immunity will last through the entire season.

Myth #8: Pregnant women should not receive the flu vaccine or must receive written consent from their doctor before doing so.

During pregnancy, women experience changes to their body that affect their immune system, lungs, and heart. These changes make them especially susceptible to contracting the flu virus so they are very much encouraged to receive the flu shot. With rare exception, it is recommended that everyone 6 months and older get a flu shot.

Rare exceptions include those with a moderate/severe illness who are advised to wait until they are recovered to get the vaccine, and those with a history of Guillain-Barré Syndrome. Guillain-Barré Syndrome is an autoimmune disease in which a person’s nervous system is attacked. It is possible a flu shot may increase your risk of developing this disease if you are already at risk for it.

Myth #9: Flu vaccines contain harmful ingredients.

There are some elements of the flu vaccine like thimerosal, used as a preservative, and formaldehyde, used in killing the live virus, that make people uncertain about getting the flu shot. Multiple studies have repeatedly shown that these substances are contained in too small a quantity in the flu shot to cause harm. Rare exceptions include those with a moderate/severe illness who are advised to wait until they are recovered to get the vaccine, and those with a history of Guillain-Barré Syndrome. Guillain-Barré Syndrome is an autoimmune disease in which a person’s nervous system is attacked. It is possible a flu shot may increase your risk of developing this disease if you are already at risk for it.

Myth #10: I have never gotten the flu before so there is no reason for me to get a flu shot.

Just because you have been fortunate over the last years to not contract the influenza virus, that does not mean that you can never get the flu. There are many individuals that have never been involved in a boating accident, but when you are on the water it is still recommended that you carry enough life preservers for everyone onboard. Getting the flu shot is a proactive step that you can take to prevent yourself from contracting the flu if you are exposed to it.

Myth #11: The only way to protect yourself from getting the flu is getting the flu shot.

This is not to say that getting the flu shot is not important. It is very important and everyone who is able should get the flu shot every year. What this does mean is that there are things that we can do in addition to receiving the flu shot that can keep you healthy during the flu season. These things include the following:

  • Avoid contact with people who have the flu
  • Wash your hands
  • Refrain from touching your eyes, nose, or mouth
  • Practice good health habits like disinfect surfaces at home, work, or school, get plenty of rest, be physically active, manage your stress, and eat nutritious foods

Sources and More Information

Center for Disease Control and Prevention, “Misconceptions about Seasonal Flu and Flu Vaccines”.

Kaiser Permanente, “10 Flu Shot Myths”.

Harvard Health Publishing, “10 Flu Myths: Dispelling Misinformation About the Flu Vaccine, Sickness, Treatment, and Recovery”.

Center for Disease Control, “Preventing the Flu: Good Health Habits Can Help Stop Germs”.
By Jeremiah Johnson, MA, BS

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