Published on September 03, 2020

A Closer Look: Getting the Facts on the Flu Vaccination

Photo of Paul Berg, M.D., president, MidMichigan Physicians Group, Midland, Michigan.

Paul Berg, M.D.

While COVID-19 has caused significant illness and concern for millions of Americans and residents across the globe, experts at MidMichigan Health remind us not to lose sight of another potentially lethal virus - Influenza.

Influenza is a seasonal virus that impacts the U.S. population each year between late fall and early spring. Since 2015, influenza has caused between 280,000 to 810,000 hospitalizations each year in the U.S., and 23,000 to 61,000 Americans have died from the virus. Fortunately, influenza is a preventable illness because of the annual flu vaccine. However, only about half of the U.S. population receives the flu vaccine each year. 

Paul Berg M.D., president, MidMichigan Physicians Group; Courtney Pearson, M.D., infectious disease specialist, MidMichigan Physicians Group, and Lydia Watson, M.D., senior vice president and chief medical officer, MidMichigan Health, answer some of the common questions about the flu vaccine:

Photo of Courtney Pearson, M.D., infectious disease specialist, MidMichigan Physicians Group, Midland, Michigan.

Courtney Pearson, M.D.

How does the flu vaccine work?
The flu vaccine works by causing antibodies to form in the human body. These antibodies provide protection against infection if that individual is later exposed to the actual virus. Vaccines in the U.S. protect against three (“trivalent”) or four (“quadrivalent”) different strains of the flu virus. Once the flu vaccine is administered, it takes about two weeks for the body to generate the protective antibodies. These antibodies then provide protection for several months following the vaccination. The best time to receive the flu vaccination is in the fall, prior to the arrival of the seasonal virus. Most medical providers begin administering the vaccine in September but will continue to administer for the duration of the flu season. The Centers for Disease Control and Prevention (CDC) recommends that people get a flu vaccine by the end of October.

Who should be vaccinated?
With rare exception, every human older than 6 months of age should receive the flu vaccine each year. Some people may not be candidates for certain vaccine types, dependent on factors such as age, allergy history, or underlying medical conditions, so these individuals should check with their medical provider to discuss which vaccine may be best for them. However, the most important fact to remember is to receive the vaccine each year.

Photo of Lydia Watson, M.D., senior vice president and chief medical officer, MidMichigan Health, Midland, Michigan.

Lydia Watson, M.D.

Does the flu vaccine really work?
Yes. The vaccine is effective, though the effectiveness can vary based on certain factors. The protection from the vaccine varies from season to season dependent on the “match” between the vaccine and the actual viruses circulating in the community. An individual’s health status can also play a role in the effectiveness of the vaccine. In general, the vaccine is most effective in young, healthy adults and older children. Older adults may not mount as robust an antibody response to the vaccine. Even though it is not perfect, the flu vaccine remains a very helpful tool in preventing serious illness from influenza. Here are some statistics to highlight the benefits of the flu vaccine:

  • In the 2018-2019 flu season, the vaccine prevented an estimated 4.4 million illnesses, 2.3 million flu-related medical visits, 58,000 flu-related hospitalizations, and 3,500 flu-related deaths. 
  • It is estimated that receiving the flu vaccine reduces a person’s risk of having to go to the doctor with flu by 40-60 percent. 
  • A 2018 study showed that, from 2012 to 2015, the flu vaccine among adults reduced the risk of being admitted to an ICU with flu by 82 percent.
  • A 2017 study showed that flu vaccination significantly reduces a child’s risk of dying from influenza.
  • Flu vaccination is very beneficial for those with underlying medical conditions, as it has been shown to reduce rates of cardiac events in those with heart disease, and reduce hospitalization rates for those with COPD, chronic lung disease, or diabetes. 
  • Flu vaccination is beneficial for those that are pregnant, as it reduces the risk of serious flu-related lung infections by 50 percent. It is also beneficial for the infant, who will have circulating antibodies protecting them from illness for several months after birth. 

Why do some people get sick with the seasonal influenza virus even though they received the vaccine?
It’s possible that some people get sick with the seasonal virus because they were exposed to the virus within two weeks of receiving the vaccine. It takes up to two weeks to develop the antibodies once vaccinated, so an exposure to the real virus during this window could still result in illness. Another reason may be that the person was exposed to a virus that was not in the seasonal vaccine. There are many different strains of the influenza virus that circulate each year. The flu vaccine is designed to protect against three or four of the most common strains that the research suggests will be circulating in the given year.

In addition, it’s possible that the person simply did not develop a good immune response to the vaccine. Some individuals, such as older adults or those with underlying health conditions, don’t develop a strong response to the vaccine. For this reason it is important that all individuals get vaccinated. The more young, healthy people that are vaccinated, the less likelihood that they will spread the virus to more vulnerable individuals.

Can the flu vaccine give me the flu?
No. The flu vaccine cannot cause flu illness. Flu vaccines that are administered with a needle (flu shots) are currently made two ways. The vaccine is either flu viruses that have been killed (inactivated) and are therefore not infectious, or they are made with proteins from a flu virus (recombinant vaccines) and cannot cause illness. Nasal spray influenza vaccines are made with attenuated (weakened) live flu viruses, and also cannot cause flu illness. The weakened viruses used in the nasal spray vaccines are cold-adapted, which means that they are designed to only cause mild infection at the cooler temperatures found within the nose. The viruses cannot infect the lungs or other areas where warmer temperatures exist.

What about side effects? 
The flu vaccines can have some side effects. Possible minor side effects include soreness or redness at the injection site, headaches, fever, muscle aches, nausea, or fatigue. Most individuals do not have these side effects. For those that do, the side effects are usually mild and short-lived. As with any medicine, there is the remote chance that people could have a serious allergic reaction or complication. This is very rare.

Shouldn’t we be more focused on COVID-19 than influenza?
We certainly need to keep our focus on COVID-19, but one way to protect our valuable health care resources is to reduce the chances of other serious infections like influenza. Ensuring that all health care workers and community members receive the flu vaccine is a great strategy to reduce the influenza disease burden in our communities. Let’s all get vaccinated for the flu, protect ourselves and our resources from that lethal virus, so we can focus on the risks that COVID will present this coming fall and winter.

How can you tell the difference between the flu and COVID-19 symptoms?
It’s going to be difficult to tell the difference between the flu and COVID-19 symptoms since both illnesses produce respiratory symptoms. In addition, it’s possible to have both infections at the same time. Testing needs to be done to determine if symptoms are due to flu or COVID-19.

Those interested in more information on the flu vaccine may visit