OBJECTIVES : Each season in France, influenza infection is responsible for an important outbreak conducting to 2-6 million GP visits and leading to several thousands of deaths. Although influenza epidemic is closely monitored by the French national public health agency (Santé publique France), the hospital burden of influenza is still underappreciated. The study objective is to describe the public health and economic burden of influenza at hospital from the season 2010/11 to 2017/18.

METHODS : Data on influenza-associated hospitalizations were extracted from the French national hospital administrative database (PMSI). The number of hospital stays and the corresponding number of hospitalized patients were determined using disease-specific ICD-10 codes (J09/J10/J11) used as main and associated diagnostic. Associated costs were estimated from the payer’s perspective, using French official tariffs.

RESULTS : Over the period, 18,979 [min: 8,627; max: 44,024] influenza hospitalizations occurred on average per season. Age distribution of hospitalized patients varied from one season to another: patients aged ≥65 years accounted for 14% of the stays in 2010/11 versus 66% in 2016/17 and 52% in 2017/18. Mean length of stay was 8.3 days, [min: 3 days; max: 10 days] with oldest patients experiencing the longest stays. On average, influenza stays cost 81,9M€ per season [min: 26,4M€; max: 209,7M€]. The mean cost of hospitalization was 4,319€ [min: 1,206€; max: 5,118€].

CONCLUSIONS : Influenza is associated with a substantial number of hospitalizations and massive costs each season. Our estimate is expected to be conservative. Additional studies including burden associated with influenza-related and associated complications are needed to have a comprehensive estimate of the burden of influenza at hospital.