Clinical outcomes of influenza in individuals aged ≤20 years before and after COVID-19: a national analysis of mortality and complications.

BACKGROUND

The COVID-19 pandemic has altered the typical annual pattern of influenza. We aim to assess its impact on influenza outcomes, especially on mortality, cardiovascular, and non-cardiovascular complications.

METHODS

This study utilized discharge records from the National Inpatient Sample (NIS) for 2019 and 2022. We analyzed the data of hospitalized influenza patients (20 years and younger) using descriptive statistics and logistic regression models.

RESULTS

29,270 influenza hospitalizations were identified in the pre-pandemic year and 29,860 in the post-mitigation year. The median age was 6 years (IQR: 2-12) in the post-mitigation year vs. 4 years (IQR: 1-9) in the pre-pandemic year, P < 0.001. Mortality and major cardiovascular complications, including myocarditis and tachyarrhythmias, showed no differences. Respiratory failure was more common in post-mitigation (21.4% vs. 12.7%), with nearly twice the risk in adjusted models [aOR = 1.92 (1.68-2.19), P < 0.001]. Invasive mechanical ventilation use decreased in the post-mitigation year by 30% [aOR = 0.7 (0.55-0.89), P = 0.004].

CONCLUSION

Mortality and cardiovascular complications remained stable in pre- and post-mitigation year; however, post-pandemic influenza showed an increased risk of respiratory failure with a decreased invasive mechanical ventilation use. This suggests a shift in disease presentation and clinical management strategies in the post-mitigation period.

IMPACT: Influenza's clinical profile in children has changed post-COVID, with increased respiratory failure and a shift to older affected age groups, while mortality and severe cardiovascular complications remain stable. This study is the first to systematically compare pediatric influenza outcomes, including all major complications and mortality, pre- and post-COVID-19, revealing specific shifts in disease presentation and demographics. Informs clinical vigilance, diagnostic strategies, and public health planning for pediatric influenza by highlighting shifts in hospitalization patterns and complications observed during the post-mitigation period. Findings support preparedness efforts recognizing temporal disruptions surrounding the pandemic.