Objectives: The effectiveness of influenza vaccine in solid organ transplant (SOT) recipients may be decreased due to immunosuppression. Some studies have suggested that influenza vaccination may decrease severity of illness in patients who become infected. The purpose of this study was to evaluate if influenza vaccination was associated with reduction in disease severity in SOT recipients hospitalized with influenza.

Methods: Adult SOT recipients hospitalized at a tertiary care medical center between 2009 and 2015 and with laboratory-confirmed influenza were enrolled. Data was prospectively collected and vaccination status was confirmed by review of electronic medical records.

Results: 51 SOT recipients hospitalized with laboratory-confirmed influenza were enrolled. 33 (64.7%) patients received influenza vaccine within the same season and at least 2 weeks prior to infection. The proportion of patients older than 65 was the same in the vaccinated and unvaccinated groups (24.2% vs. 22.2%, p=1.0, respectively). The types of transplants were: lung (n=24), kidney (n=6), liver (n=8), heart (n=7), kidney and pancreas (n=5), and liver and pancreas (n=1). All patients received influenza-directed antiviral therapy. There was no significant difference in ICU requirement (9.1% vs. 16.7%, p=0.66), occurrence of superimposed pneumonia (45.4% vs. 50%, p= 0.79), median length of stay (6 days vs.5.5 days, p=0.68), discharge to home vs. extended care (87.9% vs. 88.9%, p=0.681), hospital mortality (6% vs. 0, p= 0.53) or readmission ( 51.7% vs. 52.9%, p=0.77), when vaccinated SOT recipients were compared to unvaccinated. Superimposed pneumonia was more common in lung transplant recipients as compared to other SOT recipients; however, there was no difference in superimposed pneumonia in vaccinated vs. unvaccinated lung transplant recipients (37.5% vs. 29.2%, p=1.0).

Conclusion: Severity of illness in hospitalized SOT recipients with laboratory-confirmed influenza did not differ based on vaccination status within the same season in this single center study. A larger sample size is needed to evaluate this further.

CITATION INFORMATION: Bagenski A, Silveira F. Effect of Influenza Vaccination in the Severity of Illness in Hospitalized Transplant Recipients with Laboratory-Confirmed Influenza. Am J Transplant. 2017;17 (suppl 3).

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