Influenza infection in immunosuppressed patients: clinical characteristics, risk factors and effect of antiviral therapy

Background: Influenza infection was a vital threat to immunosuppressed patients with longer viral shedding; however, data on these populations in China are still lacking. We analyzed clinical characteristics, risk factors for admission to intensive care unit (ICU) and death, and effect of antiviral therapy in these populations.Methods: We analyzed 73 immunosuppressed inpatients tested positive for influenza virus using reverse-transcription polymerase chain reaction during the 2018-2019 influenza season. Medical data were analyzed using descriptive statistics. Univariate analysis and multivariate logistics analysis were used to identify risk factors. Results: The most common immunosuppression type was malignancies with chemotherapy 73.9% (54/73), then hematopoietic stem cell transplantation 19.2% (14/73). The most common presenting symptom was fever in 91.8% (67/73) patients, then cough 59.6% (34/57) and muscular soreness 35.1% (20/57). Complications and co-infections were found in 38.4% (28/73) and 17.8% (13/73) patients respectively, which significantly prolonged the hospital stay. Antiviral treatment after 48 hours was significantly associated with admission to ICU, mechanical ventilation and death. Combination and double dose of neuraminidase inhibitors did not significantly reduce the admission to ICU and death. 15.1% (11/73) patients were admitted to ICU and 8.2% (6/73) patients died. Risk factors for admission to ICU were long symptom onset (OR 5.60, P=0.018) and co-infection with other infections (OR 68.66, P=0.019), and presence of dyspnea was independently associated with death (OR 48.00, P=0.003) through multivariate logistics analysis. Seasonal influenza vaccination in preceding 12 months only took up 2.7% (2/73).Conclusion: Fever and other classical symptoms may be absent in immunosuppressed recipients, and conducting influenza virus detection at the first time is a good choice for early diagnosis. Antiviral treatment within 48 hours is of significance; however, patients may not benefit from combination and double dose of neuraminidase inhibitors. Immunosuppressed patients with dyspnea, long symptom onset and co-infection with other infections are of note needed, because these people have high-risk to severe cases. Inactivated influenza vaccination should be taken into account in immunosuppressed patients.