In a large, geographically diverse pediatric US population, new asthma diagnoses declined by half among children over the first 12 months of the COVID-19 pandemic. These findings underscore a dramatic change in the incidence of asthma in the US during the early phases of the pandemic, complementing other literature on pandemic-related improvements in asthma control.

Prior studies on children with pre-existing asthma documented large reductions in asthma exacerbations and asthma-related use of emergency services during the pandemic [2, 3, 6]. While the pandemic led to notable disruptions in healthcare access and delivery[1, 2], the apparent improvements in asthma control may have also occurred, in part, to lower exposures to circulating respiratory viruses, such as rhinovirus [7], and other environmental triggers[8].

In contrast to the many studies that have focused on pediatric patients and populations previously diagnosed with asthma, much less has been published on the incidence of asthma during the pandemic. To our knowledge, only one prior study has investigated new cases of asthma: a Japanese study showing declines in the number of pediatric asthma diagnoses across multiple facilities in the first 15 months of the pandemic [4]. These authors also showed a correlation between declines in asthma incidence and declines in numbers of documented cases of respiratory syncytial virus and rhinovirus. In contrast to that study, our study was population-based, performed in a general US population, estimated actual changes in incidence, and used a robust outcome definition.

Viruses such as rhinovirus are well-described triggers of childhood wheezing and subsequent diagnoses of asthma in children [9]. Notably, young children with allergic sensitization are more susceptible to rhinovirus-associated wheezing [10]. Rhinovirus infection may also predispose some children to develop asthma, particularly in the presence of certain commensal respiratory microbiota, such as Moraxella, Haemophilus, and Streptococcus.[11, 12] We posit that physical distancing and wearing of masks in the early stages of the pandemic limited exposure to and inhalation of asthma-inducing respiratory viruses. In various surveillance studies, a substantial reduction in the circulation of rhinovirus and other non-SARS-CoV-2 respiratory viruses was observed early in the pandemic, coinciding with protective measures such as lockdown and school closures [13, 14]. Given the role of pollutants in the development of childhood asthma [15], pandemic-associated declines in air pollution may also have contributed to the observed decrease in asthma incidence [16, 17].

A limitation of our study includes possible misclassification of either asthma diagnosis or newly diagnosed asthma based on our diagnostic algorithm. However, it was based on previously validated and highly accurate algorithms [5]. Additionally, our study did not include more recent data on asthma incidence in the US.