Providence, RI—COVID-19 vaccine boosters appear to be especially important for patients with blood cancers, including leukemia, lymphoma, and multiple myeloma, according to a new study.

A report in the journal Cancer pointed out that because of impaired immune systems related to both their diseases and treatment, those patients are at risk of severe COVID-19 infection as well as a reduced response to COVID-19 vaccination.

The Brown University–led researchers advised that fewer than half of patients with hematologic malignancies developed detectable antibodies after initial COVID-19 vaccination. Yet, they note, 56% of "nonresponders" produced antibodies after receiving a booster dose.

The study team retrospectively analyzed antibody responses to initial and booster COVID-19 vaccination in 378 patients with hematologic malignancies. They reported that seroconversion occurred in 181 patients (48%) after initial vaccination.

The authors noted that "patients who had active malignancy or those who were recently treated with a B-cell-depleting monoclonal antibody had the lowest rates of seroconversion."

Specifically looking at initial nonresponders to vaccination, researchers reported that seroconversion after a booster dose occurred in 48 of 85 patients (56%). They added that the seroconversion rate after the booster was similar for patients on (53%) and off (58%) active therapy (P = .82).

Of the patients overall, 33 (8.8%) developed a COVID-19 infection, and three died.

"Although no significant association was observed between postvaccination seroconversion and the incidence of COVID-19 infection, no patient with seroconversion died from COVID-19, and no patient who received tixagevimab/cilgavimab (n = 25) was diagnosed with a COVID-19 infection," the authors wrote.

The study concluded, "Booster vaccinations can promote seroconversion in a significant proportion of patients who are seronegative after the initial vaccination course regardless of the specific vaccine or on/off treatment status at the time of revaccination. Although postvaccination seroconversion may not be associated with a decrease in any (including asymptomatic) COVID-19 infection, the authors' experience suggested that effective vaccination (including a booster), supplemented by passive immunization using tixagevimab/cilgavimab in case of lack of seroconversion, effectively eliminated the risk of COVID-19 death in the otherwise high-risk population."

"Our findings build on the wealth of literature showing that patients with hematologic malignancies have an impaired response to COVID vaccination. Importantly, we show that many of these patients who did not respond initially will in fact have a response to booster vaccination," added lead researcher Thomas Ollila, MD, of Brown University in Providence, Rhode Island. "Moreover, when we looked at outcomes, we found that deaths from COVID-19 in the patient population we reviewed only occurred in those with undetectable antibodies, and nobody who received prophylactic antibody therapy was diagnosed with COVID-19. This suggests to us the importance of checking antibody levels in these patients and arranging prophylactic antibody therapy."

Dr. Ollila urged booster vaccines for blood cancer patients and prioritizing prophylactic antibody therapy when indicated, explaining, "This is real-world evidence that these actions can save lives."

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