In a Canadian study reported in the Journal of Clinical Oncology, Blanchette et al found the influenza vaccine was effective among patient with cancer, with greater effectiveness in patients with solid tumors vs those with hematologic malignancies.
The population-based study involved 26,463 adult patients with cancer who underwent respiratory testing during the 2010–2011 to 2015–2016 influenza seasons in Ontario.
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Vaccine effectiveness was determined using test-negative design, in which patients were identified as cases (influenza test–positive) or controls (influenza test–negative) on the basis of their influenza diagnostic test results. Influenza vaccine effectiveness was estimated by comparing the ratio of odds of vaccination among test-positive cases vs odds of vaccination among test-negative controls. Patients had a mean age of 70 years, 52% were male, 69% had solid tumors, and 23% received active chemotherapy.
Among the 26,463 patients who underwent influenza testing, a total of 4,320 (16%) tested positive and 11,783 (45%) had received a seasonal influenza vaccine. On multivariate analysis, adjusted vaccine effectiveness overall was 21% (95% confidence interval [CI] = 15%–26%). Vaccine effectiveness for reducing hospitalization for influenza was 20% (95% CI = 13%–26%), but reductions in intensive care admissions (vaccine effectiveness = 16%, 95% CI = –1% to 30%) and death within 30 days of specimen collection among inpatients (vaccine effectiveness = 20%, 95% CI = 0%–36%) did not achieve significance. Vaccine effectiveness for hospitalization was higher for patients aged 18 to 65 years (33%, 95% CI = 20%–44%) vs those aged > 65 years (15%, 95% CI = 6%–22%; P for interaction = .02).
Vaccine effectiveness was 25% (95% CI = 18%–31%) among patients with solid tumors vs 8% (95% CI = –5% to 19%) among patients with hematologic malignancies (P =.015). No significant difference in vaccine effectiveness was observed between patients receiving active chemotherapy (14%, 95% CI = –1% to 26%) vs those not undergoing active chemotherapy (22%, 95% CI = 15%–28%; P for interaction = .38). Among patients with solid tumors, vaccine effectiveness was 26% (95% CI = 5%–42%) among those receiving active chemotherapy and 24% (95% CI = 17%–31%) among those not receiving active chemotherapy (P for interaction = .71); among patients with hematologic malignancies, vaccine effectiveness was 1% (95% CI = –22% to 20%) among those receiving active chemotherapy and 11% (95% CI = –5% to 25%) among those not receiving active chemotherapy (P for interaction = .44).
The investigators concluded, “Our results support recommendations for influenza vaccination for patients with cancer. Vaccine effectiveness was decreased for patients with hematologic malignancies, and there was no significant difference in vaccine effectiveness among patients with solid tumor[s] receiving active chemotherapy. Strategies to optimize influenza prevention among patients with cancer are warranted.”
Phillip S. Blanchette, MD, MSc, of London Regional Cancer Program, London Health Sciences Centre and University of Western Ontario, is the corresponding author for the Journal of Clinical Oncology article.
Disclosure: The study was supported by a Canadian Institutes of Health Research grant and by ICES and Public Health Ontario, which are funded by grants from the Ontario Ministry of Health and Long-Term Care. For full disclosures of the study authors, visit jco.ascopubs.org.