Timing isn't everything: Influenza vaccination in cancer patients

Influenza vaccination is a critical intervention for improving population health and is recommended annually by the Centers for Disease Control and Prevention/Advisory Committee on Immunization Practices for all persons aged 6 months or older. In community-based studies, influenza vaccination has been shown to decrease laboratory-confirmed influenza as well as influenza-associated hospitalizations for adults, including the elderly. In addition, influenza vaccine administered to pregnant women provides subsequent postnatal protection against influenza to their infants aged <6 months. Moreover, in a pediatric study, influenza vaccination significantly decreased the risk of intensive care unit admission due to influenza virus infection. Influenza virus infection is associated with significant morbidity and mortality, particularly in high-risk individuals with underlying medical conditions, including malignancies. Studies of influenza virus infection in patients with cancer have demonstrated mortality ranging from 11% to 33%. Notably, the majority of data for this population come from patients who have a hematologic malignancy or are undergoing hematopoietic stem cell transplantation. More recently, during and after the pandemic 2009/H1N1 outbreak, adult patients with solid malignancies with pandemic influenza infection had hospitalization and mortality frequencies of 50% and 9.5%, respectively. Two studies reported similar mortality frequencies in children with malignancies. Yearly influenza vaccination is recommended by the Centers for Disease Control and Prevention/Advisory Committee on Immunization Practices and the Infectious Diseases Society of America (IDSA) as well as the American Cancer Society (ACS) for all individuals 6 months old or older, including individuals with active malignancies. Although influenza vaccination plays a central role in infection prevention in patients with malignancies, it is important to note that influenza vaccine studies in these high-risk individuals generally demonstrate impaired influenza vaccine responses in comparison with agematched healthy controls. Several interventions have been proposed to improve this immunogenicity impairment; they include the administration of a 2-dose influenza vaccine series and the use of high-dose and/or adjuvanted vaccines. Despite decreased influenza vaccine immunogenicity in patients with cancer, some studies have shown a clinical benefit related to influenza vaccination in this population. In one prospective cohort study of adult cancer patients, influenza vaccination was significantly associated with decreased mortality in a multivariate analysis. In a meta-analysis of influenza vaccination in immunocompromised patients, influenza vaccination significantly decreased the odds for influenza-like illness in patients with cancer. Finally, in colorectal cancer patients, influenza vaccination was associated with decreased influenza diagnoses, decreased pneumonia occurrence, and a decrease in the frequency of delayed chemotherapy courses. Therefore, despite the lower immune response, the benefit of receiving influenza vaccination outweighs the potential for impaired immune response. Despite the recommendation to administer the influenza vaccine to patients with cancer, the optimal timing of influenza vaccination for individuals who are undergoing active cytotoxic chemotherapy is not well delineated. Few data exist regarding the immunogenicity and safety of influenza vaccination with respect to the timing of chemotherapy administration. Notably, the IDSA recommends deferring influenza vaccination for patients receiving anti–B-cell antibody therapy (eg, rituximab) and for patients undergoing intensive chemotherapy (eg, induction or consolidation chemotherapy for leukemia patients). Both the IDSA and the ACS recommend administration of the influenza vaccine at least 2 weeks before chemotherapy, with the ACS also offering the option of vaccination between chemotherapy cycles. Primary data