Original Research

Despite the annual development of effective influenza vaccines, influenza remains a significant cause of morbidity and mortality in Canada. In the 2009–2010 influenza season, approximately 40,000 Canadians were infected with seasonal influenza or the pandemic H1N1 influenza virus,¹ and influenza has been estimated to cause 4,000–8,000 deaths in Canada each year.² It is estimated that a severe influenza pandemic could result in a 1% reduction in annual gross domestic product in Canada.³

Patients with hematologic malignancies are known to be at increased risk of influenza and its complications, with estimated mortality rates in the range 5%–27%.^{[4], [5], [6], [7] and [8]} Evidence for the efficacy of the influenza vaccine is limited and contradictory, and many assume that immunocompromised patients will not be able to generate a protective antibody response. Nonetheless, current evidence favors vaccination.⁹ Pollyea et al¹⁰ reported that eight of 15 trials on the efficacy of vaccination in patients with hematologic malignancies concluded that vaccination was beneficial. Both the Centers for Disease Control and Prevention (CDC) and the Public Health Agency of Canada (PHAC) advised that all immunocompromised patients, including those with cancer, receive both the seasonal influenza vaccine and the pandemic H1N1 influenza vaccine in the 2009–2010 influenza season.^{[11] and}