Blood Cancer Survivors Should Not Rely on COVID-19 Antibody Tests to Determine Immunity

Patients with blood cancers may be less likely to derive immunity from the COVID-19 vaccine, though antibody tests should not be the end-all-be-all in guiding their behavior.

Patients with lymphoma and chronic lymphocytic leukemia (CLL) may be more prone to COVID-19 or severe complications, though they should not use antibody tests to determine their level of protection, said Dr. John P. Leonard.

Leonard, who is the Richard T. Silver Distinguished Professor of Hematology and Medical Oncology at Weill Cornell Medicine, recently discussed the COVID-19 vaccine during a webinar hosted by the Lymphoma Research Foundation.

“Having lymphoma or CLL, even if you’re a patient who’s been never treated or on watch and wait, can be associated with a compromised, or what I call an ‘imperfect’ immune system,” Leonard said. “Patients who have gotten certain treatments, particularly multiple treatments and recent treatments might be prone to infections. They may have a diminished immune system, either with respect to antibodies or cells involved in the immune response.”

The longer a person has been off therapy, the more their immune system was likely to have recovered, explained Leonard. “And therefore, the more likely that there might be some protection from the vaccine,” he said. “Again, there are a lot of gray areas.”

Additionally, patients who are on anti-CD20 therapies like Rituxan (rituximab) or Gazyva (obinutuxumab) have depleted B cells, which aid in the creation of antibodies against COVID-19 that a person’s body makes after they receive the vaccine.

Though antibodies are a key part in protecting an individual against COVID-19, results of an antibody test should not be the only consideration when determining if a person is protected against the virus.

“If you’ve been vaccinated and you have an antibody test, you can’t use this for very much to guide how you behave,” Leonard said, explaining that labs are subjective when it comes to the threshold of determining a positive or negative test result.

Antibody tests also do not measure other factors of the immune response, according to Leonard. The tests measure the antibody protein but not the cells. Previous research showed that about 25% of patients with blood cancer did not produce antibodies after they received the COVID-19 vaccine.

“It’s not a very simple black-and-white (answer) for patients and individuals, particularly immunocompromised individuals who can be in a very middle ground,” Lenoard said. “And the middle isn’t necessarily a bad place or a safe place.”

While antibody tests may not paint the whole picture of COVID-19 immunity, Leonard did say that having detectable levels of antibodies is better than not having them.

“But how much better and how safe one is or isn’t based on these tests is very, very difficult. And these tests are not validated for decision making about anything you (should) do in relation to COVID-19 and vaccination,” Leonard said. “Don’t change your behavior based on this basis.”

Ultimately, Leonard recommends that patients with blood cancer continue to exercise precautions regarding COVID-19 infection. He also hopes that the recent FDA approval of the Pfizer vaccine will encourage more people to get the shots.

“Many people were looking toward that milestone to get vaccinated,” he said. “Many in this country are hesitant for a variety of reasons, and hopefully the FDA approval will encourage more people to become vaccinated.”

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