Blood cancers

Blood cancer patients should have vaccine booster priority, study suggests

Patients with haematological malignancies should be given the highest priority for a COVID-19 vaccine booster dose, suggest findings of a large study investigating the immune response to vaccination in people with cancer.

The prospective cohort study of COVID-19 immunity involving 585 patients with cancer, called CAPTURE and published in Nature Cancer, found that seroconversion rates after two doses of vaccine (Pfizer-BioNtech’s BNT162b2 or AstraZeneca’s AZD1222) differed significantly between patients with solid tumours and those with blood cancers, at 85% and 59%, respectively.

Patients with haematological malignancies were also more likely to have undetectable levels of neutralising antibodies (NAb) and had lower median NAb than those with solid cancers; just 31% of patients with blood cancers versus 62% of those with solid malignancies produced antibodies able to neutralise the Delta variant after both vaccine doses, the data showed.

“By comparison with individuals without cancer, patients with haematological, but not solid, malignancies had reduced neutralising antibody (NAb) responses,” noted the research team, led by Dr Samra Turajlic, Group Leader at the Francis Crick Institute and Consultant Medical Oncologist at The Royal Marsden NHS Foundation Trust.

Another key finding was that neutralising antibody responses against the Delta variant were higher in vaccinated patients with cancer who had previously been infected with SARS-CoV-2 (57% for blood cancers, 86% for solid cancers) compared to those who hadn’t (31% and 62%, respectively), which the researchers believe indicates that a third vaccine dose could boost immunity in vulnerable patients.

The study also showed that age and vaccine type were linked to immune responses: following vaccination older patients developed lower levels of neutralising antibodies, while those with solid cancers vaccinated with AZD1222 had lower responses than those who had received BNT162b2.

Most cancer treatments did not seem to affect the immune response to vaccination, though anti-CD20 therapy was linked to an absence of neutralising antibodies, and patients with chronic lymphocytic leukaemia were more likely to lack NAb than those with multiple myeloma (Delta strain, 0% versus 32%, respectively).

The researchers also found that 79% of vaccinated patients with cancer developed a T cell response, which was similar regardless of cancer type. They noted that while other clinical studies have also shown that some blood cancer patients recovered from COVID-19 did not have neutralising antibodies but did have a strong T cell response, but that the implications of this on overall immunity are not yet clear.

According to Dr Turajlic, the CAPTURE study provides evidence that SARS-CoV-2 variants of concern “pose a greater threat to some patients with cancer, specifically those with blood cancer,” and “support the argument that these people should be prioritised to receive a third vaccine dose”.

The authors also noted that “defining the correlates of immune protection (including humoral and cellular responses) will be critical to guide decision making” going forward.

On 8 October the Australian Technical Advisory Group on Immunisation (ATAGI) recommended a booster third dose of vaccine as part of the primary course in individuals who are severely immunocompromised to address the risk of suboptimal or non-response to the standard 2 dose schedule. The recommendation applies to all individuals aged ≥12 years with certain conditions or on therapies leading to severe immunocompromise, including active haematological malignancy.

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