Impact of Influenza Vaccination on Outcomes of Influenza Infections in Immunocompromised Patients

Introduction Patients with cancer are more susceptible to influenza infections than the general population, Hematopoietic Cell Transplant (HCT) recipients in particular. Conflicting data on influenza vaccine effectiveness and a lack of clear recommendations in complex clinical scenarios make the compliance with immunization suboptimal. Methods We conducted a retrospective study and included both HCT and non-HCT recipients with laboratory-confirmed influenza infection during the previous flu season (September 2017- May 2018). We evaluated 365 patients with hematologic malignancies (85), HCT recipients (138), and patients with various solid tumors (142). We analyzed the impact of influenza vaccination on mortality. Results Influenza A/H3N2 was the most common type detected during the past season with a total of 251 (69%) patients affected and half of the patients were hospitalized. Amongst the HCT recipients, more patients had an allogeneic than autologous transplant (56% vs. 44%). When compared to HCT recipients who were vaccinated, non-vaccinated HCT recipients had higher mortality rate (21% vs. 6%, p Conclusion Influenza vaccine administered to HCT and non-HCT recipients prior to a flu infection was effective in reducing overall morbidity and mortality associated with this infection. Although protection from influenza infection was suboptimal, we recommend universal vaccination during the flu season to prevent worse outcomes including mortality, especially amongst HCT recipients.