Cancer And Flu: How To Protect Yourself During Flu Season

Cancer is a terrible disease, and cancer treatment can be complicated. These patients often have problems with their immune systems. Thus, they are more likely to get influenza, and once they get infected, they are more likely to go through flu complications.

That’s why cancer patients are advised to take precautions during flu season, as they may be at higher risk of flu-related complications.

In this article, you will find what you need to know about the subject. In the end, we’re also considering a few tips and recommendations to protect yourself during the upcoming flu season.

What is an immune system?

The immune system includes a series of cells and tissues that protect you from infection. There are several lines of defense, and we can highlight two branches: innate and acquired immunity.

Innate immunity is the first line of defense. It would protect you from bacteria and viruses, even if you didn’t have a previous contact. Natural killer cells, neutrophils, eosinophils, monocytes, and basophils are all part of this system.

Acquired immunity is the second line of defense. When bacteria break the first line and colonize, acquired immunity learns about them to plan the defense. It takes a while, but finally, new molecules are formed to target critical proteins in the outer coat of bacteria or viruses. Whenever they are, if they keep displaying the same proteins, they will be attacked. It is a specialized system but not as fast as innate immunity.

The immune system can be found in the blood but also in an alternate system called lymphatic tissue. This circulatory system has lymph nodes, which house different types of immune system cells.

The importance of a strong immune system

A robust immune system is more important than we think. Even if you don’t realize it, your organism constantly interacts with millions of bacteria every day. Millions of mini-battles are conducted, and your immune system usually wins. You don’t feel a thing because the microorganisms do not get to colonize your body.

As soon as your immune system weakens, you will feel completely different. Catching a disease will be easier, but not only that. You may also experience unexpected and rare complications after getting infected. Since no immune barriers are met, bacteria keep invading and may cause life-threatening problems. An apparently harmless flu may turn into a deadly case of pneumonia. A urinary bladder infection may reach the kidneys, spread through the blood, and cause sepsis.

In a nutshell, strengthening your immune system helps your body continue working normally. You may still get infectious diseases from time to time, but the resolution will probably be easier. The main problem with cancer patients is that cancer treatment often destroys healthy cells in the process. White blood cells from the immune system are not the exception.

How cancer treatment affects your immune system

The benefits of anti-cancer treatment are due to cytotoxicity. The type of cancer treatment most likely affects your immunity is chemotherapy. It consists of administering a drug that runs in the blood and reaches every part of the body. This is basically a permanent arrest of the cell cycle and promotion of apoptosis (cell death).

Trying to target cancer, these drugs are aimed at rapidly proliferating cells. But the problem is that, besides cancer, other cells in the body divide rapidly-for example, cells in the gastrointestinal system and the bone marrow. In the gastrointestinal system, patients may experience diarrhea, nausea, and vomiting. As for bone marrow consequences, they include anemia (low red blood cell count) and immunosuppression (low white blood cell count).

Depending on the type of chemotherapeutic agent, you could have a higher or lower chance of immunosuppression. The mechanisms of immune cell destruction include (1,2):

  • Cell cycle arrest in immune cell precursors: Before immune cells are properly formed, chemotherapeutic agents stop the process of division and development. The most affected group of precursor cells is known as small lymphocyte population. This is a very early stage of immune cells, and if they stay in the same phase, mature immune cells will not form.
  • Interfering with DNA synthesis: This is what happens with alkylating agents. They interfere with DNA synthesis and new cell formation. What they do is cross-linking DNA strands. In other words, they bind DNA together very tightly. This way, it will be impossible to unroll and copy DNA. New cells are not formed, and old white blood cells are slowly broken down.
  • Endoplasmic reticulum stress in mature cells: Even mature white blood cells are affected by chemotherapeutic drugs. The endoplasmic reticulum is essential to process proteins. When this function is overwhelmed by different causes, the ER enters into a stress response. It tries to cope by preventing more proteins from reaching its structure. Chemotherapeutic drugs cause ER stress. It is so severe that coping mechanisms are insufficient, and cells start to give out danger signals. Stressed cells are marked with an “eat me” signal, and dendritic cells destroy them.

What is flu?

Flu is the short name of influenza, one of the most common respiratory infections. It is a contagious ailment caused by an airborne (respiratory) virus. It usually reaches and infects the throat and nose. However, it may sometimes reach the lungs. Depending on where it is located and how far it goes, it can cause a very mild or rather severe illness.

The most common flu symptoms include fever and chills, dry cough, a runny nose, and sore throat. Patients may also display tiredness, headaches, and muscle aches. In children, influenza may also cause diarrhea and vomiting. This is different from catching a common cold, which rarely causes fever. Instead, common symptoms mainly include sneezing and a stuffy nose. COVID 19 symptoms are similar to those found in influenza, so it is recommended to report your symptoms if you have them.

Influenza has a seasonal spread. In the United States, influenza cases range from 3 to 11%, according to data shared by the CDC. That’s why a new influenza vaccine is elaborated every year containing the new flu strains of each upcoming flu season (3). 

How flu can affect your immune system

Once influenza reaches the respiratory epithelium, it starts replicating. Depending on the susceptibility of your cells and your immune system, it may cause mild disease or a systemic spread with multiorgan failure. The latter is not the most common but causes severe respiratory distress and life-threatening illness. The immune system is involved in what type of disease your organism develops.

According to the CDC, in the 2019-2020 season, there were up to 56 million cases of flu. Around 740,000 patients were hospitalized, and 62,000 of them died due to complications. Based on these statistics, the mortality rate is approximately 0.11. However, it depends on a variety of risk factors. Immunity problems deserve special consideration in this regard.

When immunity cannot handle the flu virus, it is more likely to invade the lower respiratory tract. When influenza reaches the alveoli of the lungs, the risk of severe symptoms is higher. It compromises gas exchange, and the flu virus is exposed to endothelial cells and the blood. In this step, the immune system could contribute to the flu virus instead of destroying the invaders. The responding immune system causes damage to the alveoli, obstruction of the airways, and destruction of the extracellular matrix. The collapse of the epithelial layer is imminent, either from direct influenza infection or this error by the immune system.

These patients progress to pneumonia, and they may experience respiratory distress. It happens to 30 to 40% of patients. The higher risk is found in very young and senior patients, immunocompromised, and people with a history of smoking or chronic lung disease

When the epithelial layer is breached, antibodies are the only way to stop influenza from traveling throughout the body. Thus, immunocompromised patients will likely suffer from a higher degree of complications.

In extreme cases, influenza may also lead to sepsis. This is generalized inflammation that destroys blood vessels and causes circulatory damage. Several parts of the body undergo edema, and organs start to fail. In this case, the risk of mortality is exceptionally high (4).

Flu in cancer patients

As noted above, a depressed immune system is a risk factor for infection. It also increases the rate of mortality in patients with influenza. Thus, cancer patients are at considerable risk and need influenza vaccination as soon as possible. It should be a flu vaccine based on inactivated influenza (5).

There are not many studies or clinical trials of influenza in cancer patients. Most studies try to elucidate the best practices of applying vaccines to this population. However, one article published in the journal Cancer studied the cancer population as a whole using the CDC statistics on the U.S. influenza virus.

The study showed that 24% of hospitalized cancer patients with influenza complications have lung carcinoma. Another 20% of them have hematologic malignancies. 75% of them were in the age group of 65 and older. They usually had other health problems, and the most common were heart disease, lung disease, kidney disease, liver problems, and diabetes.

The highest mortality rate was found in patients with lung malignancy and hematologic cancer. Their death risks were 12% and 9%, respectively, and they spent an entire week in the hospital (5).

How to protect yourself during flu season

As a cancer patient, you should get recommendations very seriously during flu season. According to the CDC, this is what everybody should do to prevent flu:

  • Get the flu vaccine: This flu shot is renewed every year with the most active variants of the virus. It is probably the most crucial step to prevent this infection and its consequences. Flu shots are recommended for cancer patients as they can help reduce the risk of hospitalization and improve overall health outcomes. Cancer patients are at a higher risk of complications and should be a priority. Still, talk to your doctor to ensure that the current flu shot contains the type of inactivated influenza you need.
  • Prevent infections in your everyday life: After coronavirus, most of us know how respiratory illnesses spread and how to prevent them. What you have learned these years also apply to influenza infections. The essential recommendation is avoiding close contact with symptomatic patients. Washing your hands often and disinfecting surfaces. Avoid hand contact with your mouth, nose, and eyes.
  • If you’re infected, take medications as prescribed: Your doctor may recommend antiviral medicines in these cases to manage flu symptoms and reduce the risk of complications in some cases. They are more recommended for people with risk factors, and cancer is one of them.


Seasonal influenza has been around for many years, and a recent flu outbreak was the prelude to the current worldwide pandemics. While we get the recent COVID 19 vaccine, flu season is now starting in northern countries.

Cancer patients are particularly at risk of getting influenza. Moreover, their immune system is compromised by the disease or its treatment. Thus, flu effects are more severe in this population. They often need antiviral drugs, and prevention with flu vaccination is fundamental.

Still, care is advised for all, especially during these trying times. We recommend reporting any type of flu like symptoms, even if you don’t have cancer. Remember that COVID 19 patients should have a special treatment to prevent complications.

If you’re a cancer patient, take your time to get a flu shot. Stay on guard with respiratory diseases, and report new symptoms to your doctor as soon as possible.

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  1. Gebremeskel, S., & Johnston, B. (2015). Concepts and mechanisms underlying chemotherapy induced immunogenic cell death: impact on clinical studies and considerations for combined therapies. Oncotarget, 6(39), 41600.
  2. Rasmussen, L., & Arvin, A. (1982). Chemotherapy-induced immunosuppression. Environmental health perspectives, 43, 21-25.
  3. Tokars, J. I., Olsen, S. J., & Reed, C. (2018). Seasonal incidence of symptomatic influenza in the United States. Clinical Infectious Diseases, 66(10), 1511-1518.
  4. Kalil, A. C., & Thomas, P. G. (2019). Influenza virus-related critical illness: pathophysiology and epidemiology. Critical care, 23(1), 1-7.
  5. Cooksley, C. D., Avritscher, E. B., Bekele, B. N., Rolston, K. V., Geraci, J. M., & Elting, L. S. (2005). Epidemiology and outcomes of serious influenza‐related infections in the cancer population. Cancer: Interdisciplinary International Journal of the American Cancer Society, 104(3), 618-628.

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