# Changes in Pediatric Acute Respiratory Infections Before, During, and After the COVID-19 Pandemic: A Retrospective Study

## TL;DR

This study shows how public health measures during the pandemic reduced and changed the timing of childhood respiratory infections, which later increased beyond pre-pandemic levels.

## Contribution

The study quantifies how pandemic interventions altered pediatric respiratory infection trends and their post-pandemic rebound.

## Key findings

- Pediatric ARI incidence dropped during the pandemic and rose sharply afterward, surpassing pre-pandemic levels.
- Atypical inter-seasonal peaks occurred during the pandemic, but disease severity remained stable.
- Non-respiratory infections were unaffected by pandemic measures.

## Abstract

Introduction and objectives: Acute respiratory infections (ARIs) are a significant cause of morbidity in children and a common reason for emergency department (ED) visits. During the COVID-19 pandemic, governments adopted non-pharmacological interventions (NPIs) to limit SARS-CoV-2 transmission. These measures also reduced the circulation and seasonality of other respiratory pathogens, with little impact on infections in non-respiratory organ systems. This study aimed to quantify changes in the incidence and severity of pediatric ARIs before, during, and after the pandemic.

Materials and methods: We conducted a retrospective observational time-series study of children aged 0-10 years presenting with ARIs to a level 2 pediatric ED in Covilhã, Portugal, from April 2019 to April 2023. To ensure representativeness while controlling data volume, admissions from the first five days of each month were analyzed. Three periods were defined: pre-COVID-19 (Pre-C), COVID-19 (C), and post-COVID-19 (Post-C). All statistical analyses were performed using SPSS Statistics version 28 (IBM Corp. Released 2021. IBM SPSS Statistics for Windows, Version 28.0. Armonk, NY: IBM Corp.). A significance level of p = 0.05 was applied.

Results: Among 7,448 sampled ED visits, 2,210 (29.7%) involved ARIs. Their proportion fell from Pre-C to C (p = 0.028) and rose sharply in Post-C (p < 0.001), exceeding Pre-C levels (p < 0.001). In C, atypical inter-seasonal peaks occurred. Hospitalization rates, length of stay, and oxygen requirements showed no significant variation.

Conclusions: COVID-19 NPIs were associated with a marked reduction and altered timing of pediatric ARIs, whereas infections in other organ systems were largely unaffected. After restrictions were lifted, ARI incidence surpassed pre-pandemic levels, but disease severity remained stable. These findings highlight how public health measures and subsequent exposure shifts can reshape respiratory infection epidemiology in children.