Incidence, severity, and clinical characteristics of lower respiratory tract infections in children before and after the coronavirus disease 2019 lockdown: a Dutch single-center study

Purpose: Coronavirus disease 2019 (COVID-19) public health measures reduced the incidence of pediatric lower respiratory tract infections (LRTIs) in 2020. An inter-seasonal surge in the LRTI has occurred after relaxation of restrictions. We aimed to compare characteristics and disease severity of children with LRTI before, during, and after COVID-19 lockdown. Methods: All LRTI-related visits to emergency department (ED) of a large pediatric hospital in the Netherlands between 2019 and 2021 were included. Variables were compared between 2019 and 2020, and between 2019 and 2021, respectively. The variables included demographic characteristics, condition upon ED arrival, diagnosis, applied treatment, and follow-up.Results: In 2019, 2020, and 2021, numbers of the visits were 573, 280, and 519, respectively, comprising the study population (n = 1,372). In 2020, the patients were older, and showed higher frequencies of preterm birth history, co-occurring symptoms of obstructive lung disease, and salbutamol therapy in the ED, than in 2019. In 2021, the patients were younger, showed higher frequencies of desaturation, bronchiolitis, co-occurring symptoms of obstructive lung disease, salbutamol therapy, and hospitalization, and showed lower frequencies of respiratory ED visits or hospitalization in the past year, and antibiotic therapy. During hospitalization in 2020, the patients were older, and showed shorter duration of oxygen support and length of hospital stay, as well as lower frequencies of nasogastric tube insertion, compared to 2019. In 2021, compared to 2019, the patients showed a higher frequency of bronchiolitis and lower frequencies of underlying medical conditions and antibiotic therapy. Conclusion: The children presenting with LRTIs in 2021 seem to have had a more severe clinical phenotype, possibly explained by immunity debt after the COVID-19 lockdown, stricter referral policy, or changes in healthcare-seeking behavior. Future research is needed to evaluate the long-term consequences of growing up during the lockdown.