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Atopic outcomes at 2 years in the CORAL cohort, born in COVID-19 lockdown
Sadhbh Hurley1,2, Ruth Franklin1, Naomi McCallion1,3
1Paediatrics and Child Health, Royal College of Surgeons, Dublin, Ireland.
Insights
Infants born during COVID-19 lockdown experienced higher rates of atopic dermatitis but lower rates of food allergies. This suggests the altered early-life environment may influence allergic condition development.
Area of Science:
- Immunology
- Pediatrics
- Epidemiology
Background:
- The COVID-19 pandemic lockdown created a unique early-life environment for newborns.
- This environment was characterized by reduced antibiotic exposure, increased breastfeeding, and fewer infections.
- These factors may influence the development of allergic conditions in infants.
Purpose of the Study:
- To investigate the incidence of allergic conditions in infants born during the COVID-19 lockdown.
- To compare allergic outcomes in a lockdown cohort (CORAL study) with a pre-pandemic cohort (BASELINE).
Main Methods:
- A longitudinal observational study followed 365 infants from birth to 2 years.
- Infants underwent assessments at 6, 12, and 24 months, including skin prick testing and atopic dermatitis evaluation.
- Data were compared with a pre-pandemic cohort.
Main Results:
- Higher incidence of atopic dermatitis (AD) was observed in the CORAL cohort at 12 and 24 months compared to the BASELINE cohort.
- Despite higher AD, food allergies (milk, peanut, egg) were less common in the CORAL group.
- Aeroallergen sensitization and wheezing episodes increased between 12 and 24 months in the CORAL cohort.
Conclusions:
- The lockdown environment, despite increasing AD, may protect against food allergies, potentially due to altered infant infections and early allergen introduction.
- These findings challenge the traditional hygiene hypothesis by suggesting potential benefits from reduced microbial exposure.
- The study highlights the complex interplay between early-life environment and allergic disease development.
Introduction:
The CORAL study is a cohort of infants born during the first weeks of the first SARS-CoV-2 (COVID-19) lockdown. This cohort has had lower antibiotic exposure, higher breastfeeding rates and lower infection rates, especially in the first year of life. We hypothesized that the altered early-life environment of infants born during lockdown would change the incidence of allergic conditions.
Methods:
This longitudinal, observational study followed 365 infants born between March and May 2020 from enrolment to the age of 2 years. Infants attended three research appointments at 6-, 12-, and 24-months and completed detailed questionnaires. At research appointments, children had skin prick testing, and atopic dermatitis (AD) assessment. Statistical analysis focused on changes within the group at different time points, the influence of specific environmental factors on allergic risk and compared the incidence of atopic conditions with a pre-pandemic Irish infant cohort, BASELINE.
Results:
AD was more common in CORAL group at both 12 (26.5% vs. 15.5%; p < .001) and 24 months (21.3% vs. 15.9%; p = .02) compared with pre-pandemic BASELINE cohort. Within the CORAL group, those with AD at both 12- and 24-month appointments had a more severe AD phenotype associated with a higher risk of allergic sensitization. There was less milk (0% vs. 1%; p = .09), peanut (0.6% vs. 1.8%; p = .3), and egg allergy (0% vs. 2.9%; p < .001) in the CORAL group at 24 months compared with the BASELINE cohort. Aeroallergen sensitization increased between 12 and 24 months in the CORAL cohort (1.5% vs. 8.9%; p < .001), as did parent-reported wheezing episodes (9% vs. 24%; p < .001).
Conclusions:
Despite higher AD incidence in the CORAL cohort, the incidence of food sensitization and allergy are lower than expected pre-pandemic rates possibly reflecting the early introduction and maintenance of dietary allergens enhanced by changes in infant infections, antibiotic use, and breastfeeding in the first 2 years of life in the group. These beneficial effects of the lockdown could be outweighing the expected risk of less early-life microbial encounters outlined by the hygiene hypothesis.
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