Most adults with blood cancer mount immune responses after receiving a booster dose of the COVID-19 vaccine, according to a study.

People with hematologic malignancies or blood cancers including leukaemia, lymphoma, and multiple myeloma have an impaired immune system due to their disease and its treatment, putting them at risk of severe COVID-19 infection and experiencing a reduced response to vaccination.

The study, recently published in the journal CANCER, found that less than half of patients with hematologic malignancies mounted detectable antibodies after initial COVID-19 vaccination, but 56 per cent of "nonresponders" produced antibodies after receiving a booster dose.

"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," said Thomas Ollila from Brown University in the US.

"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," Ollila said in a statement.

The researchers analysed antibody responses to initial and booster COVID-19 vaccination in 378 patients with hematologic malignancies. Anti-SARS-CoV-2 antibodies were detected in the blood of 181 patients (48 per cent) after initial vaccination with one of three approved COVID-19 vaccines in the US, they said.

Patients with active cancer or those recently treated with an immune cell-depleting therapy were least likely to produce these antibodies, the researchers said. Among patients who did not mount an antibody response following initial vaccination, responses were observed after a booster dose in 48 of 85 (56 per cent) patients who were assessed, according to the study.

By the end of February 2022, 33 patients (8.8 per cent) developed a COVID-19 infection, with three COVID-19-related deaths (0.8 per cent). Although there was no significant link between post-vaccination antibody response and incidence of COVID-19 infection, no patient with antibody responses died from COVID-19, the researchers said.

No patient who received antibody therapies tixagevimab plus cilgavimab was diagnosed with a COVID-19 infection, they said. Tixagevimab and cilgavimab bind to non-overlapping portions of the SARS-CoV-2 spike protein, preventing the virus from binding to and infecting cells.

Ollila advised providing booster vaccines for patients and prioritising prophylactic antibody therapy when indicated. "This suggests to us the importance of checking antibody levels in these patients and arranging prophylactic antibody therapy. This is real-world evidence that these actions can save lives," he added.