Sustained Increase in Pediatric Mastoiditis in the Post-COVID-19 Era in France: A 9-Year Interrupted Time-Series Analysis.

Objective: To assess the impact of COVID-19 pandemic-related, non-pharmaceutical interventions (NPI) on the incidence of mastoiditis cases, causative pathogens, and associated complications in children.

Study design: We conducted a population-based, interrupted time-series analysis using national surveillance data from France between January 2016 and December 2024. All hospitalized mastoiditis cases among individuals younger than 18 years in France were included. The main outcome was the monthly incidence of mastoiditis cases, analyzed using quasi-Poisson regression models, accounting for seasonality.

Results: We included 7390 hospitalized cases of mastoiditis in children. Following a decrease in the incidence of mastoiditis by 58.9 % (95% CI: 68.2% to 46.9%, p <0.001) during the strict NPI period, we observed an increase of 71.7% (95% CI: 26.4% to 133.3%, p <0.001) in the post-NPI period compared with the expected trend without NPI. The proportions of complicated cases and those requiring surgery remained stable over time. By pathogen, the most important increase in the post-NPI period was observed among mastoiditis caused by Streptococcus pyogenes (627.8%, 95% CI: 269.1% to 1335.0%, p <0.001), followed by Streptococcus pneumoniae (135.6%, 95% CI: 20.5% to 360.6%, p = 0.012) and Haemophilus influenzae (+124.3%, -17.0% to 506.0%, p = 0.111).

Conclusions: In this 9-year, population-based national study, we observed a sustained increase in the incidence and etiology of mastoiditis in children during the post-COVID-19 period. We hypothesize that these changes, associated with NPI during the pandemic and lifting post-pandemic, reflect consequences that should be considered in management of future pandemics.