# Association Between Fine Particulate Matter (PM2.5) and Severity of Acute Respiratory Infections Among Young US Children in the Major Cities in the United States: A Claims-based Cohort Study

## TL;DR

This study finds that short-term exposure to fine particulate matter (PM2.5) increases the severity of respiratory infections in young children, with influenza vaccination potentially reducing this risk.

## Contribution

The study provides new evidence linking PM2.5 exposure to severe respiratory outcomes in children and highlights the protective role of influenza vaccination.

## Key findings

- Short-term PM2.5 exposure increases antiviral prescription claims by 11% among young children.
- Influenza-unvaccinated children show a 6% higher risk of ICU admission with PM2.5 exposure.
- Influenza vaccination may reduce the severity of PM2.5-related respiratory outcomes in children.

## Abstract

Acute respiratory infections (ARIs) are a leading cause of morbidity and mortality among children. Air pollution may play a role in the exacerbation of ARIs via inflammation, immunosuppression, and oxidative stress, yet this effect has been infrequently evaluated among children.

Evaluate the impact of short-term exposure to fine particulate matter (PM2.5) to ARI severity among US children aged <5 years.

We analyzed data from a claims-based cohort of children included in a private health insurance plan (Merative™ MarketScan® Commercial Claims and Encounters database) who were diagnosed with an ARI between January 2018 and March 2020. We use daily monitored PM2.5 concentrations at the metropolitan statistical area level to estimate the short-term weekly PM2.5 exposure. We evaluated the association between short-term PM2.5 exposure and the risk of prescription claim for antiviral medication, hospital admissions and readmissions for an ARI, intensive care unit (ICU) admission for an ARI, mechanical ventilation, and length of stay among hospital-admitted and ICU-admitted children using generalized linear models.

The risk of an antiviral prescription claim increased by 11% (95% confidence interval, 1.07-1.15) per interquartile range increase in PM2.5 exposure (3.34 µg/m3); this association was consistent regardless of age, biological sex, and influenza vaccination status. We observed a 6% increased risk of ICU admission (95% confidence interval, 1.02-1.10) among children not vaccinated against influenza and no increase among vaccinated children.

Short-term PM2.5 exposure may contribute to ARI severity among children. Influenza vaccination may modify the risk of severe ARI-associated outcomes.

Suggestive evidence that short-term exposure to PM2.5 increases the risk of severe acute respiratory infection outcomes in young children. Influenza vaccination status may modify the impact of short-term exposure to PM2.5 leading to milder respiratory illness in young children.