Factors associated with influenza vaccination among adult cancer patients: a case-control study

Influenza vaccination is recommended for cancer patients; however, adherence is low. We aimed to identify predictive factors for vaccination among cancer patients. We conducted a case-control analysis of a patient cohort in the 2010-2011 influenza season. We included adult cancer patients with solid malignancies undergoing chemotherapy, and haematological patients with active disease. Patients who died between October and November 2010 (N = 43) were excluded from analysis. Cases received the 2011 seasonal influenza vaccine, and controls did not. Data were obtained from patients' records, and validated through personal interviews. We collected socio-demographic information, and data on the malignancy and co-morbidities and triggers for vaccination and non-vaccination. We performed bivariate and multivariable analyses, in which vaccination status was the dependent variable. Of 806 patients included in analysis, 387 (48%) were vaccinated. Variables associated with vaccination on bivariate analysis were older age, higher socio-economic status, lower crowding index, marital status (widowed > married > single), malignancy type (haematological > solid tumours) and time from diagnosis, low-risk malignancy, diabetes, past vaccination, country of birth (non-Russian origin), and physicians' recommendations. Predictive factors found to be independently associated with vaccination on multivariable analysis were past vaccinations, low-risk malignancy, and country of birth. In the analysis conducted among interviewees (N = 561), recommendations from the oncologist (OR 10.7, 95% CI 5.4-21.2) and from the primary-care physician (OR 3.35, 95% CI 2.05-5.49) were strong predictors for vaccination. We conclude that 'habitual vaccinees' continue influenza vaccinations when ill with cancer. Physicians' recommendations, especially the oncologist's, have a major influence on patients' compliance with influenza vaccination.