Blood cancers

Seasonal flu vaccine less effective in people on chemotherapy


Seasonal influenza vaccine is less effective in patients receiving cancer drugs and has a short duration of protective response that may not last the flu season, Australian research has found.

A study of immune responses to trivalent flu vaccine in 53 patients with non-haematological cancers on active treatment with chemotherapy and targeted therapy found that seroconversion rates for the three flu strains were below the threshold 40% level in criteria for vaccine effectiveness.

The patients had predominantly breast, colorectal and gynaecological malignancies and were receiving cancer treatment such as chemotherapy, monoclonal antibodies and  tyrosine kinase inhibitors. They were given vaccine while on active treatment, with the immunisation timed to be at a point furthest away from the next treatment dose.

In the study, conducted at Flinders Medical Centre, Adelaide, the early seroconversion  (postvaccination ≥ 4-fold increase in HIA titre )rates at 3 weeks for cancer patients receiving trivalent vaccine were 35%, 30% and 22.5% to H1N1, H3N2 and B/Bris strains, respectively.

While the primary endpoint for early seroconversion was not met, the more clinically meaningful endpoint of seroprotection (percentage of individuals with a serum HIA titre ≥ 1:40) was achieved in > 60% of the patients.

At three weeks postvaccination, seroprotection was 72.5%, 65.0%, 40.0%, respectively, to the H1N1, H3N2 and B/Bris component of the vaccine. Current criteria for vaccine recommends SPR in at least one strain in > 70% (or > 60% if > 60 year).

Seroprotection rates at 24 weeks were lower (40.0%, 52.5% and 17.5% to H1N1, H3N2 and B/Bris, respectively)  and the overall sustained SPR to any vaccine component was 49%. There were no cases of late seroconversion.

The study authors said the lower seroconversion rates for flu vaccination  during cancer treatment might be due in part to some patients being on chronic steroids. The novel findings of a decline in seroprotective titres at 24 weeks also suggested that if this occurred the end of the influenza season end, patients would face in an increased risk of influenza

The findings, published in Supportive Care in Cancer, suggested there may be merit in a other strategies to boost or maintain seroprotective titres beyond the influenza season such as booster doses, they said.

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