(255) Evaluating the Cardioprotective Effects of Antivirals in Influenza Patients: A Retrospective Cohort Study.

Background: Studies have linked influenza infection to acute cardiovascular events like myocardial infarction, stroke, and heart failure exacerbations. Influenza antivirals (AVs), such as oseltamivir, zanamivir, and baloxavir, when administered early in the course of infection, can mitigate the severity and duration of symptoms, thereby potentially reducing the risk of cardiovascular complications associated with influenza.

Objectives: To evaluate the protective effect of influenza AVs against major adverse cardiovascular events (MACE) in adults.

Methods: A retrospective cohort study was conducted using the Merative MarketScan Commercial Claims and Encounters and Medicare Supplemental databases. Adults (≥18years) with an outpatient influenza diagnosis (their first in the study period) from October 1, 2016, to June 30, 2021, were included. Continuous enrollment for 1 year prior to this diagnosis was required. Those who received an influenza AV on the diagnosis day were classified as treated. Exclusion criteria included a MACE within 30 days before the influenza diagnosis. Baseline comorbidities and medications were identified using diagnosis and dispensing data from the year preceding the diagnosis. Influenza season specific propensity scores were used to balance the groups. The outcome of interest (MACE) was defined as a composite of myocardial infarction, stroke, heart failure, and acute coronary syndrome. Follow-up continued until the first of the following event: MACE related inpatient admission, disenrollment, study end, or 30 days post-influenza diagnosis. Patients who did not receive AVs on diagnosis day but did later were censored at that time point. Cox proportional hazards regression was used to compare risk of MACE between treated and untreated individuals.

Results: 1,086,326 influenza episodes were included, with 658,707 receiving an AV on diagnosis day. The average age was 42 years, and 58% were female. The 2017-18 season represented over 30% of cases. Common comorbidities included hypertension, hyperlipidemia, obesity, and diabetes. After PS matching, each group consisted of 411,862 individuals. MACE incidence was 18 per 1000 person-years in the untreated group and 12 in the treated group. The treated group had 33% lower MACE risk (HR: 0.67, 95% CI: 0.59-0.76).

Conclusions: Influenza AVs exhibited a protective effect against MACE events during the follow-up period. However, these findings should be interpreted with caution due to the potential for channeling bias when comparing treated group with an untreated group. Further studies using different designs, including case-based methods, are needed to confirm the findings of this study.