Respiratory Morbidity Before and During the COVID-19 Pandemic from Birth to 18 Months in a Swedish Birth Cohort.

Background: Respiratory infections in early life is one identified risk factor for asthma. We hypothesized that infection preventive measures during the COVID-19 pandemic influenced the risk of respiratory morbidity and aeroallergen sensitization in early childhood.

Objective: To compare respiratory morbidity and aeroallergen sensitization in children born before and during the pandemic.

Methods: We compared a COVID-19 category i.e., exposed children (n = 1661) to a pre-COVID-19 category i.e., non-exposed children (n = 1676) by using data from the prospective population based NorthPop Birth Cohort Study in Sweden. Data on respiratory morbidity and concomitant medication were retrieved from national registers. Prospectively collected data on respiratory morbidity using web-based questionnaires at 9 and 18 months of age were applied. At age 18 months, serum immunoglobin E levels to aeroallergens were determined (n = 1702).

Results: The risk of developing any respiratory tract infection (aOR = 0.33 [95% CI = 0.26-0.42]), bronchitis (aOR 0.50 [95% CI = 0.27-0.95]) and croup (aOR = 0.59 [95% CI = 0.37-0.94]) were decreased in the COVID-19 category. The risk of wheeze in the first 9 months was lower in the COVID-19 category (aOR = 0.70 [95% CI = 0.55-0.89]). There were also lower prescriptions of antibiotics in the COVID-19 category. The prevalence of aeroallergen sensitization was similar between the categories.

Conclusion: Children born during the COVID-19 pandemic demonstrated significantly decreased risks of respiratory infections and prescribed antibiotics until 18 months of age compared to children born before the COVID-19 pandemic. Whether this will impact the risk of developing asthma in childhood is being followed.