People with certain blood cancers, including chronic lymphocytic leukemia (CLL), have impaired immune systems. This means developing COVID-19 can have more serious implications. Experts still recommend the COVID-19 vaccine.

Throughout the COVID-19 pandemic, medical professionals cautioned that people with compromised immune systems had a higher chance of severe illness if they contracted the virus.

While vaccination paved the way for something of a “return to normal” for much of the world, new data suggests that some people — like those with leukemia — still need to take certain precautions to prevent serious illness.

Scientists have developed several vaccinesagainst COVID-19 over the last few years. Because these vaccines are so new, little data has been available on how well they work among people with various health conditions.

Over the last several years, a number of studies have been published that take a closer look at the response in people with blood cancers, including CLL.

People with CLL and other types of leukemia already carry a higher chance of severe illness or even mortality if they develop COVID-19. This is because cancer impairs the immune system.

As vaccines against COVID-19 were under development, researchers tested them in generally healthy adults. As more groups become vaccinated, there’s more evidence on specific populations, like people with compromised immune systems.

Recent study data

B cells are critical to fighting COVID-19. These are the immune cells that can neutralize the virus and help produce antibodies. People with CLL are at an increased risk when it comes to COVID-19 because B cells are the type of immune cells most affected by this specific type of blood cancer.

A 2021 study found that people with CLL vaccinated with Pfizer’s mRNA COVID-19 vaccine had an antibody response rate of 39.5%. In generally healthy adults, this rate is around 90%.

Individual response rates varied among people with CLL based on their disease progression and treatment. Response rates in different groups of people with CLL included:

  • 79.2% response rate in people in clinical remission from CLL
  • 55.2% response rate in people with CLL who hadn’t yet received treatment
  • 16% of people with CLL who were undergoing treatment at the time of COVID vaccination

While response rates were generally low in people with CLL receiving treatment at the time of vaccination, the type of treatment further affected these rates.

People treated with Bruton’s tyrosine kinase (BTK) inhibitors had a 16% response rate to the vaccine, while those treated with venetoclax ± anti-CD20 antibody had just a 13.6% response rate. No one treated with anti-CD20 antibodies during the 12 months before their COVID-19 vaccination developed an immune response, according to the study.

Other factors also affected how well people with CLL responded to the vaccine. Researchers found that the people with CLL who had the best responses to the vaccine:

  • were younger
  • were female
  • weren’t receiving active treatment for CLL
  • had immunoglobulin (types of antibodies) G levels of 550 milligrams per deciliter (mg/dL) or higher
  • had immunoglobulin (types of antibodies) M levels of 40 mg/dL or higher

A more recent study published in late 2022 found that 42% of people with CLL who were vaccinated developed the antibodies needed to fight COVID-19. The study noted that 32% had no response.

The study suggests that people with CLL may be better suited to alternative vaccination strategies. For example, a high dose flu vaccine, typically used in older people, might produce a better immune response in people with CLL who have impaired immunity.

Above all, preventing COVID-19 in people with CLL is a top priority, according to the study’s researchers.

While the 2022 study found 32% of people with CLL who were fully vaccinated against COVID-19 didn’t have immune responses to the virus, leading cancer organizations still recommend that people with CLL receive some type of COVID-19 vaccine.

The Leukemia and Lymphoma Society (LLS) advises people with blood cancer to stay up-to-date on the latest COVID-19 vaccine. People with compromised immune systems — including those who have or have had blood cancer — can get vaccinated regularly.

If you have CLL, ask your healthcare team about a vaccination strategy.

Extensive research has not yet studied the effect of the various COVID-19 vaccines on specific populations. However, early data on people with blood cancers suggest the vaccine is safe.

While it may not be as effective as in people without blood cancers, the vaccine can offer at least some protection against COVID-19. The LLS stresses the dangers of COVID-19 for people with CLL and supports vaccination in people with this condition.

The LLS also recommends people with CLL or other blood diseases who experience COVID-19 symptoms discuss taking Paxlovid with their healthcare professional as the medication can shorten the duration of the illness — and the severity of symptoms.

Vaccines from Pfizer and Moderna are all believed to be safe for people with CLL, unless they have an allergy or other contraindication to the vaccine.

Although vaccination can offer some protection against COVID-19 for people with CLL, experts suggest that anyone with blood cancers — especially those undergoing active treatment — continue to take precautions, even after being fully vaccinated. Precautions include:

If you live in places with a high prevalence of COVID-19 transmission, your treatments may be modified or delayed to protect against infection. You and your doctor should make these decisions based on your location, specific condition, and risk factors.

The COVID-19 vaccine is recommended for anyone with CLL, as it still offers a level of protection. If you have CLL, it’s important to continue taking precautions, like wearing a mask and avoiding crowds, even after you’ve received the latest booster.

If you have questions or concerns about whether the vaccine is right for you, ask about this at your next medical appointment to find out what might work best.