What People With Cancer Should Know About Coronavirus

Medically Reviewed by Dan Brennan, MD on January 02, 2023
6 min read

If you have cancer now or have had it in the past, you have an “underlying medical condition” or “pre-existing condition” that can put you at higher risk for serious problems if you become infected with the new coronavirus.

Your immune system may not be as strong as it was before cancer. Many cancer treatments make the immune system weak. And other things, like stress, diet changes, and sleep problems, can also impact your immune system.

A weakened immune system makes it harder for you to fight infections, including a coronavirus infection. It also makes you more likely to have complications if you do become infected.

The best thing you can do is try to keep from getting infected with the new coronavirus. Follow these precautions to help lower your risk. Encourage the people you live with to do the same:

  • Keep at least 6 feet of space between yourself and other people.
  • Stay at home as much as you can.
  • When you do go out, avoid crowds.
  • Wear a face mask.
  • Use a tissue when you cough or sneeze, then throw it away and wash your hands. Or cough into your elbow instead of your hand.
  • Wash your hands often and for at least 20 seconds. Be sure to wash your hands after coughing, sneezing, or blowing your nose. Also wash them after you’ve been in a public place.
  • If you can’t use soap and water, use a hand sanitizer that contains at least 60% alcohol. Rub it on all parts of your hands and let it air dry.
  • Try to not touch your eyes, nose, or mouth unless you’ve just washed your hands.
  • Clean all surfaces you touch a lot, like doorknobs, phones, keyboards, and such. Use regular household cleaning spray or wipes.

Many experts recommend that, in general, people with cancer should get a COVID-19 vaccine. But though COVID-19 vaccines seem to be quite safe for most people with cancer, they may be less effective, especially if your immune system is weakened by your disease or treatments. There have not yet been studies to prove this because the first studies have been on people with normal immune systems. But scientists know that, in general, vaccines are often less effective in people with weaker immune systems.

Certain cancers, like leukemias and lymphomas, for example, can lead to a weakened immune system. And some cancer treatments weaken immune response too, like:

  • Chemotherapy (chemo)
  • Radiation
  • Stem cell or bone marrow transplant
  • Immunotherapy 

Keep in mind that the very thing that makes the vaccine less effective (a weak immune response) also puts you at higher risk for serious disease from COVID-19. That’s why many experts suggest you get the vaccine even if it may be less effective. Some protection, they say, is better than none at all. But even with the vaccine, if you have a weakened immune system, you may need to take extra precautions like masking, social distancing, and avoiding crowds, even when general recommendations loosen.

Booster shots

The CDC now suggests getting additional doses (sometimes called boosters) of Pfizer and Moderna vaccines for people with “moderately to severely” weakened immune systems, at least 28 days after the second dose. There is also now a bivalent booster that can target both the original COVID-19 virus and the Omicron variant.

Having a “moderately to severely weaken immune system could mean that you:

  • Are taking medicine to suppress your immune system
  • Are having treatment for blood cancer or cancerous tumors
  • Have had a stem cell transplant in the last 2 years
  • Are getting treatment with drugs known to suppress immune response, like high-dose corticosteroids

Swollen lymph nodes

Though it is safe, the COVID-19 vaccine can sometimes enlarge lymph nodes like certain cancers are known to do. This typically goes away after a few days or weeks. It’s important to tell your health care team about the timing of your vaccine and about any swelling you notice so they don’t confuse it with the spread of disease. This is especially important if it happens around the time of an imaging test like an MRI or a CT scan or a mammogram. 

Safety of vaccines

A note on vaccines in general: It’s true that in some cases, doctors recommend against certain vaccines (not COVID-19) for people who have weakened immune systems. But these are typically vaccines made with live viruses. The COVID-19 vaccines available in the U.S. (Pfizer, Moderna, Novavax, and Johnson & Johnson) do not contain live viruses.  Still, cancer is a complex and varied disease and each case is different. That’s why, if you have cancer or a history of cancer, it’s best to check with your doctor first before you get any new vaccine or medication.   

If you’re in cancer treatment now, talk to your cancer treatment team about what you should watch for and when you should call them. Be sure you know how to reach them after office hours, on weekends, and on holidays.

If you’ve finished your cancer treatment, ask your primary care doctor about health questions and symptoms.


  • Try to be extra careful about following the recommendations made by the CDC to help lower your risk of infection.
  • Stay away from anyone who appears to be sick.
  • Make sure you have enough medication at home. This includes prescription and over-the-counter drugs. Try to have at least a 1-month supply. You may want to switch to mail-order delivery so you don’t have to go out to get your prescriptions.
  • Make a list of emergency numbers that you might need so you have them all in one handy place, just in case.

The coronavirus situation changes often, so keep up with the news and latest guidelines, without letting it stress you out too much. Also, make sure you stay in touch -- from a safe distance -- with loved ones. Try to get some exercise, if you’re up to it, and get outside for a break. That’s fine to do, as long as you stay at least 6 feet away from other people. Your health is about more than your cancer, so take care of your mental and emotional health, as well as your physical health, during this especially stressful time.

Chemotherapy affects the whole body, including the immune system. These medications that kill cancer cells also lower your number of white blood cells, which fight infection. There are times in your treatment cycle when your white blood cell counts are lowest; this is when you’re at highest risk for infection. Your blood counts are checked often during treatment. So your treatment team can tell you when you’re at greatest risk. Still, do what you can to help prevent infection all the time.

Other types of cancer treatment -- such as radiation, immunotherapy, targeted therapy, and surgery -- can affect your immune system, too. Talk to your cancer care team about your treatment plan, how it impacts your risk for infection, and what you need to do during the coronavirus pandemic.

Cancer treatment is very important. You’ll want to weigh the benefits of treatment against your risks from the new coronavirus. Ask your doctor about your options to help you decide what to do about your cancer treatment during this time.

If you’ve been diagnosed with cancer but haven’t started treatment yet, you might be able to wait with some kinds of cancer, but other kinds need to be treated right away. Talk with your doctor to better understand your cancer, how fast it’s growing, and how treatment might impact your risk for infection.

Health care centers, hospitals, and doctors are doing everything they can to help limit the spread of the virus. This might change some things about your cancer treatment routine.

For instance, you might not be allowed to bring a support person with you into the clinic, you may have to answer a series of questions before you’re allowed into the building, or your treatment may be rescheduled so fewer people get treatment at the same time to allow for safe distances between them.

Some providers are using video conferencing and telemedicine to do visits while also limiting in-person contact. Changes seem to come up every day. Talk to your cancer care provider to find out what’s best for you.