People with CLL/SLL have a weakened immune system due to CLL/SLL itself, which can make them vulnerable to infections. While many CLL/SLL treatments can further affect immune function and increase infection risk, there is one class of CLL/SLL treatments -- called anti-CD20s -- that are specifically engineered to attack the very cells that house the cancer, which are also the immune cells that fight infection.
Anti-CD20 antibodies are a targeted therapy for CLL/SLL that eliminates B cells, which ironically is a type of cell that makes up the immune system. Anti-CD20-based treatments can help treat cancer, but they can also have significant, long-lasting effects on the immune system, which may make it harder to fight off infections. This matters during fall and winter – when flu, COVID-19, respiratory syncytial virus (RSV), and cold viruses circulate – because both during and after treatment with an anti-CD20, the body fights viruses less well and responds poorly to vaccines.
This does not necessarily mean that anti-CD20-based treatments are the wrong choice, but it does mean that the timing of treatment, infection prevention steps, and vaccine planning deserve careful consideration with your care team.
How Flu Season Affects People on Anti-CD20 Treatment
B cells, which are immune cells that are targeted by anti-CD20 treatments, can remain at low levels for many months after completing treatment, which means that the body cannot fight infection as well as it normally would. B-cell loss can make viruses harder to clear, which means that respiratory infections may hit harder after anti-CD20-based treatments, possibly resulting in longer hospital stays, serious complications, and/or higher death rates from COVID-19. In addition, vaccines may not work as well after anti-CD20-based treatments.
Considerations for Initiating Anti-CD20 Treatment in Flu Season
Whether to start or delay an anti-CD20-based treatment during flu season is a question to raise with your doctor as a shared decision, not something to decide on your own. When treatment for CLL/SLL is not urgent, your healthcare team may be able to fit in important vaccines before starting treatment, which may help improve your response to certain vaccines. When treatment for CLL/SLL is urgent, consider discussing the benefits and risks of available treatment options with your healthcare team, including how treatment choice may affect infection risk and vaccine timing.
Vaccine Planning and How Anti-CD20 Treatment May Change Vaccine Timing
Vaccines are recommended in CLL/SLL to lower the risk of severe illness. Receiving anti-CD20-based treatment may affect both the timing of vaccination and how well your body responds to certain vaccines. Always talk with your healthcare team about vaccine planning.
Questions to Ask the Healthcare Team
- How are we accounting for flu season risk given treatment with an anti-CD20?
- Is there another treatment choice that may be right for me during flu season?
- What can we do to minimize risk of infection during flu season?
- What vaccines do you recommend for me? On what timeline?
- Are there any other health conditions I have that may affect my treatment choice during flu season?
Minimizing Infection Risk
Please see Infections and CLL: What to Know and Understanding Infection Risk with CLL/SLL Treatment for more information about managing infection risk, including:
- Washing hands often, or using hand sanitizer when hand washing is not available
- Considering wearing a well-fitting mask in crowded indoor spaces during flu and COVID season
- Avoiding close contact with people who are sick
- Asking everyone in your household to stay up to date on their own vaccines
Contact your care team right away if you have:
- Fever (ask your team what temperature threshold to use)
- New or worsening cough or shortness of breath
- Shaking chills, or feeling very unwell
- Symptoms of flu, COVID, or RSV
This information is for general education and does not replace the personalized advice of your own care team. Your treatment and vaccine plan will be adjusted based on your specific situation and timing.
