BackgroundInfluenza is a potential inducer of acute cardiac events. However, the incidence of influenza in patients admitted to a C-ICU, the accuracy of clinical suspicion and the compliance of influenza vaccination of high-risk patients, are not well known. Objectives: To evaluate the incidence of influenza at C-ICU admission during influenza season, the potential underdiagnosis and the vaccination rate.MethodsProspective study at a tertiary institution including all patients admitted to a C-ICU during 2017–2018 flu season. A nasopharyngeal swab was collected at admission from all patients who consented (198/201, 98.5%) and tested using Xpert® Flu/RSV assay. Clinical data were registered.ResultsInfluenza was detected in 14/198 (7.1%) patients (11 FluA, 3 FluB) and initially suspected by the cardiologist in 57.1% cases. When compared with patients without influenza, flu-positive patients had more respiratory (21.4% vs. 6.0%, P = 0.03) or neurologic diseases (21.4% vs. 4.3%, P < 0.01), contact with relatives with flu-like illnesses (35.7% vs. 14.4%, P = 0.03), antimicrobials use (71.4% vs. 36.4%, P = 0.01) and need for mechanical ventilation (28.6% vs. 3.3%, P < 0.01). Reasons for C-ICU admission between both groups were similar. All patients promptly received oseltamivir and no patient with flu died (0 vs. 3.8%, P = 0.46) despite a high rate of severe presentations (85.7%) and related complications (78.6%). Seasonal flu vaccination was received by 44.9% of the patients admitted to the C-ICU and 52.0% of patients who had indication for flu vaccination. The incidence of influenza in the vaccinated and non-vaccinated population (with flu vaccine indication) was, respectively 12.6% vs. 4.1% (P = 0.08). Flu episodes in vaccinated patients required less mechanical ventilation (20% vs. 75%, P = 0.05) and showed a trend toward shorter length of in-hospital stay (6 vs. 15d, NS). Risks factors for no vaccination despite indication were: younger age (67 vs. 75y-o, P < 0.05) and less comorbidity (Charlson index 4 vs. 5, P < 0.01).ConclusionSeven percent of patients admitted to the C-ICU had influenza, only half of the influenza cases diagnosed were suspected at admission and only half of the patients with indication for flu vaccination, received the vaccine. A clinical score to recognize influenza in these patients is needed.Disclosures All authors: No reported disclosures.