Influenza prevention and treatment in transplant recipients and immunocompromised hosts.

The host immune response is critical for the control and clearance of influenza virus after initial infection. Unfortunately, key components of the innate and adaptive responses to influenza are compromised in solid organ and hematopoietic stem cell transplant recipients. As a result, influenza in these key patient populations is associated with prolonged viral shedding, more frequent complications, including bacterial and fungal superinfections and rejection, and increased mortality. While vaccine is the critical prophylaxis strategy in other populations, response rates are diminished, particularly early post-transplant, among immunocompromised patients. Prospective data suggest that antiviral prophylaxis represents an effective and safe alternative to vaccine in patients who would be predicted to have poor responses to influenza vaccine. While there have not been randomized, controlled studies of antiviral therapy completed in solid organ or hematopoietic stem cell patient populations, observational data suggest that early therapy is associated with reduced rates of progression to lower airway involvement, morbidity, and mortality. Further studies are needed to define the optimal regimen, dose, duration, and endpoint to define successful treatment.