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The COVID-19 pandemic had an upside for lockdown babies: substantially less wheezing and bronchiolitis, according to an Italian retrospective cohort study.

One or more wheezing episode by age 30 months was observed in 44% fewer babies born while stay-at-home orders were in effect compared with of those born during the same months in 2016 and 2017 (9.4% vs 15%, P<0.001), reported researchers led by Carlo Giaquinto, MD, of the University of Padua, Italy.

Wheezing episodes occurred at a rate of 67.6 per 10,000 person-months among the lockdown group and 110.0 per 10,000 person-months in the historical group, according to the research letter published in.

Bronchiolitis cases, one of the most common reasons for hospitalizations among infants, dropped drastically during COVID-19 pandemic lockdowns as well, from 82.4 episodes per 10,000 person-months in the historical cohort to just 6.6 episodes per 10,000 person-months for lockdown babies.

This decline in cases is likely tied to the social distancing measures that were in place at the time, reducing exposure to pathogens like respiratory syncytial virus (RSV), which accounts for anywhere from 50-80% of bronchiolitis cases, the researchers noted. RSV is also a known risk factor for asthma and similar wheezing illnesses.

For wheezing, 30% of the reduced risk was estimated to be due to the lockdown preventive measures alone.

The findings add weight to the recent U.S. based INSPIRE population-cohort study showing that dodging RSV infection within the first year of life was linked to a 26% lower risk of asthma over 5 years.

The new study "underscores the potential role of a universal RSV immunoprophylaxis in preventing post-bronchiolitis wheezing," Giaquinto's group argued.

After decades without an option for protecting most infants against the annual respiratory scourge, a spate of RSV prophylaxis options have become available in recent years. The maternal RSV prefusion F protein vaccine (Abrysvo) gained a recommendation last year for mothers at 32 to 36 weeks' gestation to prevent lower respiratory tract RSV infection in infants. And around the same time, the monoclonal antibody nirsevimab (Beyfortus) gained official recommendation for all infants younger than 8 months born during or entering their first RSV season.

Giaquinto's study utilized the Pedianet database for all patients seen by 150 participating family pediatricians in Italy. Wheezing and anti-asthma medication use were identified through administrative codes.

The analysis included 2,192 births during the lockdown period, spanning February to April in 2020, and 3,889 births in the historical winter bronchiolitis seasons from February to April in both 2016 and 2017. There were no differences in sex, area deprivation index, gestational age, or family history of atopic disease between the two cohorts.

Incidence curves for 30-month cumulative wheezing revealed a significant difference between the lockdown and historical cohorts, which was confirmed in a sensitivity to account for possible delayed diagnosis during lockdowns. At 45 months of age, children in the historical group had a cumulative wheezing risk of 16% compared with a risk of 13% for those in the lockdown group (P=0.002).

Additionally, children who were born during lockdown received less nebulized β₂ agonists at a rate of 5.1 per 1,000 person-months, compared with 7.9 per 1,000 person-months in the historical control group (P<0.001). The same was true for nebulized glucocorticosteroids (19.5 vs 23.5 per 1,000 person-months, P<0.001).

Limitations of the study included its retrospective design, as well as an inability to assess possible RSV infection among participants.

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