Background:

Seasonal influenza infection may cause significant morbidity and mortality in transplant patients. However, there are limited prospective data on clinical presentations and determinants of outcomes. The purpose of this study was to prospectively assess the epidemiology of influenza infection post-transplant and determine risk factors for severe disease.

Methods:

22 Centers in the U.S., Canada and Spain prospectively enrolled solid organ transplant (SOT) or stem cell transplant (HSCT) patients with microbiologically-proven influenza during five influenza seasons (2010-15). Demographics, microbiology data, and outcomes were collected.

Results:

We enrolled 511 patients with confirmed influenza (403 SOT; 108 HSCT). Mean age was 50.7±17.7 years and 4.9% were pediatric. Types of transplant were kidney(32.9%), lung(21.7%), heart(11.5%), liver(12.3%), HSCT(21.1%). Clinical presentations included fever(66.1%), cough(86.7%) and myalgias(38.0%). Pneumonia at presentation was seen in 123/498(24.7%). Most infections (80.1%) were influenza A. Antiviral therapy (oseltamivir) was given to 93.8% for a median of 5 days (range 1-24). 74.1% patients were hospitalized and 13.4% required ICU care with 10.8% needing mechanical ventilation. Factors predictive of pneumonia included HSCT vs. SOT (p=0.04), use of mycophenolate (p=0.015), and delayed initiation of antiviral therapy (p=0.002). Receiving influenza vaccine in the same season was associated with a reduced likelihood of pneumonia (19.7% in vaccinated vs. 35.3% in unvaccinated; p<0.001). Factors associated with ICU admission included delayed antivirals (p=0.036), lack of vaccination (p=0.019), and influenza strain A vs. B (p=0.044). In a multivariate analysis, lack of vaccination (p=0.001; OR 2.68 [1.53-4.68]) and delayed antivirals (p=0.005; OR 2.28 [1.28-4.09]) were predictors of pneumonia as well as ICU admission (p=0.009; OR 2.46 [1.25-4.85] and p=0.03; OR 2.46 [1.09-5.55] respectively.

Conclusions:

We performed the largest evaluation of influenza infection in transplant patients. We show that annual vaccination and early antiviral therapy are protective against severe sequelae of influenza.

CITATION INFORMATION: Kumar D, Cordero E, Blumberg E, Limaye A, Levi M, Danziger-Isakov L, Englund J, Husain S, Silveira F, Reid G, Sharma T, Humar A. A 5-Year Multicenter Evaluation of Seasonal Influenza Infection in Transplant Recipients. Am J Transplant. 2016;16 (suppl 3).

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