In‐hospital incidence of and risk factors for influenza‐associated respiratory failure

Background Respiratory failure (RF) is the most important complication of influenza virus infection. Its definition and incidence are heterogeneous in the literature. Methods This systematic review and meta‐analysis aim to determine the incidence of and risk factors for RF in patients hospitalized with influenza. Electronic databases were searched for articles on RF in patients hospitalized for influenza infection up to December 2021 regardless of their geographical location. Observational and experimental studies were considered for inclusion, excluding case series. The Newcastle‐Ottawa and Johanna Briggs scales were used for quality assessment. A random‐effects meta‐analysis was performed, followed by subgroup analyses according to, among others, presence/absence of pneumonia, RF definition, serotype and time period. PRISMA guidelines were followed for this review. Results Thirty‐six studies were finally included in the meta‐analysis. Overall, RF incidence was 24% (range 5%–85%, 95% confidence interval [95CI] 19%–31%). Significantly higher incidences of RF were found in patients with pneumonia (42%, 95CI 28%–57%, p = .006), when RF was defined as hypoxemia (58%, 95CI 31%–81%, p