- D3.526 - Baseline demographic characteristics and early-life exposures in infants born during and after the COVID-19 pandemic: A comparison of the CORAL and FLORAL birth cohorts

Early-life environmental exposures, including microbial diversity, infections, antibiotic use, and breastfeeding, are known to influence allergic disease risk. The 2020 CORAL birth cohort demonstrated lower food allergy rates in infants born during COVID-19 lockdowns, potentially reflecting altered early-life exposures. FLORAL 2025 (FoLlow on from CORAL)  is a post-pandemic birth cohort designed to examine whether these exposures and baseline characteristics differ following re-establishment of typical early-life environmental and microbial exposures post-lockdown.

FLORAL is a prospective observational birth cohort recruiting infants born from three Dublin maternity hospitals between March and May 2025. Parents consented shortly after birth and completed an enrolment questionnaire, with follow-up questionnaires completed at 6 months of age. Of 574 consented infants, 530 participants completed the questionnaire; after applying exclusion criteria, 489 participants were included in the final analysis and 440 completed the 6-month questionnaire. Identical baseline demographic characteristics and early-life exposures at 6 months were compared with the 2020 CORAL birth cohort. 

Infants in the FLORAL cohort had higher rates of hospitalisation and antibiotic exposure by 6 months compared with the CORAL cohort, however repeated antibiotic exposure was lower. Baseline demographic characteristics were otherwise similar between cohorts (Table 1). Vaccination uptake at 2 and 4 months was high in both cohorts, while uptake of 6-month vaccinations among age-eligible infants was lower in the FLORAL cohort. Rates of exclusive breastfeeding were similar in the CORAL and FLORAL cohorts (38%), while combined breast and formula feeding was more common in the FLORAL cohort (21% vs 15%). Rates of maternal smoking were low, and just over half of infants were delivered by spontaneous vaginal delivery.

Despite broadly similar demographic characteristics, the CORAL and FLORAL cohorts differ in key early-life exposures during the first 6 months, including rates of hospitalisation, antibiotic exposure, and uptake of scheduled vaccinations. These differences likely reflect broader contextual changes associated with the post-pandemic return to routine social interaction and healthcare utilisation. The FLORAL cohort is being followed longitudinally at 12 months and 2 years, enabling direct comparison with the CORAL cohort to assess allergic outcomes over time.