Patients undergoing cancer treatment at greater risk of contracting breakthrough Covid infections: Study

Patients with hematologic cancer, which begins in blood-forming tissue, and those receiving active treatment for any kind of cancer are at a greater risk of contracting breakthrough Covid-19 infections, particularly those who receive anti-CD20 therapy, according to a study.

Scientists also found that the third Covid-19 vaccine dose was associated with lower infection rate and coronavirus complications, except for patients receiving anti-CD20 therapy.

The study conducted by University of Toronto, Institute for Clinical Evaluative Sciences, St Michael's Hospital-Unity Health and Sunnybrook Health Sciences Centre, Toronto, Canada has been published in the Journal of the American Medical Association (JAMA) Oncology.

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Patients receiving cancer treatment and those with hematologic cancer, regardless of the treatment status, should be prioritised for booster vaccination, pre-exposure prophylaxis and, in the event of SARS-CoV-2 infection, early antiviral therapy, the study said.

Patients with cancer are known to have an increased risk of COVID-19 complications including death.

According to the study, a total of 2,89,400 vaccinated patients with cancer, 39,880 hematologic and 2,49,520 solid, with 11,57,600 matched non-cancer controls were identified. The cohort was 65.4 per cent female and the mean age was 66 years.

SARS-CoV-2 breakthrough infection was higher in patients with hematologic cancer, but not in patients with solid cancer.

Covid-related severe outcomes, including hospitalisation and death, were significantly higher in patients with cancer compared to patients without cancer. The risk of severe outcomes was higher among patients with hematologic cancer than patients with solid cancer, the study said.

The objective of the study was to determine the association of Covid-19 vaccination with breakthrough infections and complications in patients with cancer compared to non-cancer controls, it said.

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The study was a retrospective population-based cohort study using linked administrative databases in Ontario, Canada, in residents aged 18 and above who received Covid-19 vaccines.

Three matched groups were identified based on age, sex, and type and date of vaccine.

There was a 1:4 match for patients with hematologic and solid cancer to non-cancer controls with hematologic and solid cancers separately analysed. There was a 1:1 match between patients with hematologic and patients with solid cancer, the study said.

Outcomes occurring 14 days after the second COVID-19 vaccine dose were taken into account. The primary outcome was SARS-CoV-2 breakthrough infection and secondary outcomes were emergency department visit, hospitalisation and death within four weeks of SARS-CoV-2 infection with the end of the follow-up period being March 31, 2022.