Experts: Blood Cancer Patients Should Receive a Booster COVID-19 Vaccine

The Leukemia & Lymphoma Society (LLS) is encouraging blood cancer patients who received either the Pfizer or Moderna mRNA COVID-19 vaccine to get a third dose.

The LLS’s recommendation aligns with the Centers for Disease Control and Prevention’s (CDC) booster guidelines for people who are moderately-to-severely immunocompromised.

Why Patients Need Boosters

Data collected by the LLS showed that about one in four blood cancer patients will not form detectable antibodies to COVID-19 after receiving two doses of the Pfizer and Moderna vaccines.

The reason for the dulled response is because the medications that are used to treat blood cancers often suppress the immune system, which in turn weakens its response to the vaccine.

In a press release on September 13, Lee Greenberger PhD, chief scientific officer for the LLS, said that “antibodies tell us that a patient has responded to vaccination—and that is a positive finding, but vaccine experts are still working to determine exactly what antibody level is needed to protect against COVID-19 infection or its worst outcomes.”

LLS investigators published follow-up research in the journal Cancer Cell showing that 55% of the patients who had no response to the first two doses of the Pfizer or Moderna vaccines did develop antibodies after receiving a third dose.

Furthermore, all of the patients that originally developed some antibodies against COVID-19 after receiving the first two vaccines had an even higher level of antibodies after the third dose.

However, Gwen Nichols, MD, the chief medical officer for LLS and one of the study’s authors, says that it is not yet known what level of antibodies provides full protection against COVID-19; still, any gain in antibodies is beneficial.

Anti-CD20 and BTK Inhibitor Therapies

The researchers discovered that two classifications of medications that are used in complement to blood cancer treatment (including to treat NHL and CLL) can diminish a person’s response to the COVID-19 vaccine.

• CD20 monoclonal antibodies, or anti-CD20 antibodies. These medications are designed to attack CD20, a unique protein on the surface of B lymphocyte cells. The most common anti-CD20 antibody is rituximab (Rituxan). In addition to NHL and CLL, rituximab can also treat rheumatoid arthritis (RA) and multiple sclerosis (MS).
• Bruton tyrosine kinase (BTK) inhibitors. BTK inhibitors stop an enzyme that signals B lymphocytes to reproduce (Bruton tyrosine kinase or BTK). Stopping reproduction of the B lymphocytes prevents them from proliferating, which in turn can slow the progression of NHL and CLL. Three BTK inhibitors are currently approved: ibrutinib (Imbruvica), acalabrutinib (Calquence), and zanubrutinib (Brukinsa).

Nichols highlights that neither class of medications selectively targets diseased B lymphocytes; both therapies have a broad effect on all B lymphocytes. Therefore, anyone taking these medications will have fewer healthy B lymphocytes than people who do not take them.

“Nothing in this paper suggests that you should stop your cancer therapy in order to get an antibody response to the vaccinations,” says Nichols. “If stop your medication and your lymphoma comes back, you’re in equally bad shape, so you should not stop it without talking to your doctor.”

When to Get a Booster

The CDC is advising that patients receive the third dose at least four weeks after getting their second dose of one of the mRNA COVID vaccines.

Nichols says that patients who had COVID-19 antibody testing showing that they have developed immunity in response to the vaccine can wait until six to eight months after their second dose to get a booster shot.

“Not everybody knows whether they made antibodies, but I don’t think there’s any harm in getting it sooner,” says Nichols. “If you know that you had no antibodies please get it as soon as you can, but if you made antibodies, you should get it at six to eight months because it will last longer.”

Future Research

The LLS Patient Registry has collected data on more than 11,000 blood cancer patients. Nichols acknowledges that this is "really a small number of patients" and that it is "a preliminary study," but it's still a good start.

As more patients contribute to the registry, researchers will gain a better understanding of how blood cancer patients respond to vaccines and will be able to make recommendations that will improve care for all people with blood cancer.

“The good news is, a lot of the patients are getting boosters and are giving us information about the boosters," says Nichols. "So we should have data on hundreds of more patients over the next few months.”

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