Age-dependent rebound in asthma exacerbations after COVID-19 lockdown.

Background: Virus mitigation measures enacted early in the coronavirus infectious disease 2019 (COVID-19) pandemic suppressed common respiratory viruses and reduced the number of obstructive lung disease exacerbations. However, many localities began to ease these precautions in the year 2021, leading to a resurgence of non-COVID viruses. How asthma and chronic obstructive pulmonary disease (COPD) activity responded to this upswing in viral abundance is unclear. Objective: Our aim was to examine how viral resurgence during the relaxation of COVID-19 restrictions affected asthma and COPD exacerbations. Methods: We analyzed electronic medical records for emergency department (ED) respiratory virus positivity, asthma visits, and COPD visits. We compared the 52-week interval before the COVID-19 restrictions (the pre-lockdown period [March 22, 2019-March 19, 2020]), the 52-week period immediately following enactment of the restrictions (the lockdown period [March 20, 2020-March 18, 2021]), and the 52-week period thereafter (the post-lockdown period [March 19, 2021-March 18, 2022]). We used MetaCYCLE to analyze seasonal trends in our data. Results: The post-lockdown period was marked by a 400% increase in viral positivity compared with during the lockdown period. Asthma- and COPD-related ED visits each rose 37% compared with during the lockdown, with the rebound in asthma ED visits concentrated in individuals younger than 20 years. Interestingly, after the lockdown period, asthma ED visits overcorrected in children younger than 5 years, rising 81% compared with before the lockdown. Seasonal rhythms in asthma and COPD exacerbations were suppressed during the lockdown and recovered after the lockdown. Conclusions: COVID-19 precautions had the unexpected effect of magnifying early-childhood asthma activity once common respiratory viruses recurred. These results may have implications for the future use of virus mitigation strategies in young children.