The Latest COVID-19-associated Croup Rate in Children: A Retrospective Cohort Study from the TriNetX US Collaborative Networks

Background: Croup (laryngotracheobronchitis) is the most common pediatric disease often associated with viral infection. The incidence of croup was also high during the coronavirus disease 2019 (COVID-19) pandemic. Materials and Methods: This retrospective cohort study is based on the TriNetX US Collaborative Network. Cases were patients with croup and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection confirmed by positive ribonucleic acid findings or other related diagnoses, whereas controls were participants with croup but no evidence of COVID-19. The hazard ratio (HR) of incident croup was calculated for the case and control groups, and the 95% confidence interval (95% CI) was considered evidence of statistical significance. Results: Among the COVID-19 group, 854 patients developed croup within 7 days after the diagnosis of COVID-19 (HR = 2.77, 95% CI = [2.44, 3.15]). The incidence of croup was higher in the first 3 days after the diagnosis of COVID-19. Compared with the non-COVID group, the highest risk ratio was between 5 and 7 years of age (HR = 4.37, 95% CI = [2.87, 6.64]). The highest incidence was during the Omicron wave, followed by the Alpha and Delta waves. The risk of croup was highest from January 2023 to June 2023 (HR = 5.40, 95% CI = [3.52, 8.28)]). Conclusion: Our results showed that the incidence of croup caused by the SARS-CoV-2 virus did not decrease due to the weakening of the virus. It is also because the subsequent COVID-19 virus is of the Omicron subtype. Therefore, in children with croup, and especially those over 5 years of age, SARS-CoV-2 virus infection should still be taken into consideration.