Chemotherapy can weaken your immune system by reducing levels of infection-fighting white blood cells. If your white blood cell count is too low, it can increase your risk of getting COVID-19.

Chemotherapy, or chemo, is one of the most common treatments for cancer. However, one of the known side effects of chemo is that it can weaken your immune system.

Because chemo can impact the immune system, you may be wondering if people who are having chemo are at a higher risk of getting COVID-19. Keep reading as we explore this question and more.

Chemo drugs target the process of cell growth and division. Because cancer cells grow and divide more quickly than many other cells in your body, chemo predominantly targets cells that replicate quickly. When a cell cannot properly divide, it dies.

However, chemo can also affect healthy cells. This is particularly true for cells that divide more rapidly. Cells in the bone marrow are one example. They will become infection-fighting white blood cells called neutrophils.

Having a low level of neutrophils is called neutropenia, and it can increase your risk of contracting infections. Neutrophil levels are typically lowest in the 7–12 days after each dose of chemo and can remain low for up to a week.

While chemo is the most common cause of a weakened immune system in people receiving cancer treatment, it’s important to know that the exact effect of chemo on your immune system can depend on many factors, such as:

  • the type and dose of chemo drug(s) used
  • how often you have chemo
  • the type of cancer you have and how advanced it is
  • your age and overall health

One 2020 study found that chemo itself was not associated with severe COVID-19. However, having low white blood cells or low neutrophil counts prior to or at the time of a COVID-19 diagnosis was associated with less than favorable outcomes.

Several other studies have found that receiving chemo in the weeks prior to a COVID-19 diagnosis was not linked with a higher risk of death due to COVID-19.

Factors associated with a less optimistic COVID-19 outlook in people having cancer treatment were:

If you’re receiving chemo and contract COVID-19, your treatment may be delayed until your symptoms resolve or you no longer have a positive COVID test.

There are also several medications that can help prevent serious COVID-19 illness, including:

Your doctor will make treatment decisions based on your individual situation. There’s currently no evidence that having COVID-19 will impact the effectiveness of your cancer treatment.

If you’re currently receiving chemo, there are several steps that you can take to help lower your risk of getting COVID-19:

  • Stay up to date on your COVID-19 vaccines and encourage your family, friends, and caregivers to do so as well.
  • Avoid contact with people who currently have, or are suspected to have, COVID-19.
  • Wash your hands frequently and properly. Use hand sanitizer if soap and water are not available.
  • Regularly disinfect high-touch surfaces in your home, such as doorknobs, light switches, and faucet handles.
  • Move activities outdoors or increase ventilation in your home if possible. Avoid crowded areas or indoor locations with poor ventilation.
  • Consider wearing a mask and practicing physical distancing when you’re outside of your home.

If you develop symptoms of COVID-19, take a COVID-19 test right away. If the test is positive, isolate yourself and contact your doctor for recommended next steps.

Chemo can weaken your immune system by lowering the number of infection-fighting white blood cells you have. If your white blood cell count is too low, you may be at an increased risk of getting COVID-19.

If you’re receiving chemo and contract COVID-19, your treatment may be delayed until you recover. Your doctor may also prescribe medications to help prevent a serious infection.

If you’re receiving cancer treatment, it’s important to take steps to help prevent COVID-19. This includes staying up to date on your COVID-19 vaccines, avoiding contact with those who are sick, and washing your hands properly and frequently.